This image is released under a CC BY-NC-SA 4.0
Licence
License this image for commercial use at Science and Society Picture Library
LicenseThis image is released under a CC BY-NC-SA 4.0
Licence
License this image for commercial use at Science and Society Picture Library
LicenseThis image is released under a CC BY-NC-SA 4.0
Licence
License this image for commercial use at Science and Society Picture Library
LicenseThis image is released under a CC BY-NC-SA 4.0
Licence
License this image for commercial use at Science and Society Picture Library
LicenseThis image is released under a CC BY-NC-SA 4.0
Licence
License this image for commercial use at Science and Society Picture Library
LicenseThis image is released under a CC BY-NC-SA 4.0
Licence
License this image for commercial use at Science and Society Picture Library
LicenseThis image is released under a CC BY-NC-SA 4.0
Licence
License this image for commercial use at Science and Society Picture Library
LicenseThis image is released under a CC BY-NC-SA 4.0
Licence
License this image for commercial use at Science and Society Picture Library
LicenseThis image is released under a CC BY-NC-SA 4.0
Licence
License this image for commercial use at Science and Society Picture Library
LicenseThis image is released under a CC BY-NC-SA 4.0
Licence
License this image for commercial use at Science and Society Picture Library
LicenseThis image is released under a CC BY-NC-SA 4.0
Licence
License this image for commercial use at Science and Society Picture Library
LicenseThis image is released under a CC BY-NC-SA 4.0
Licence
License this image for commercial use at Science and Society Picture Library
LicenseThis image is released under a CC BY-NC-SA 4.0
Licence
License this image for commercial use at Science and Society Picture Library
LicenseThis image is released under a CC BY-NC-SA 4.0
Licence
License this image for commercial use at Science and Society Picture Library
LicenseThis image is released under a CC BY-NC-SA 4.0
Licence
License this image for commercial use at Science and Society Picture Library
LicenseThis image is released under a CC BY-NC-SA 4.0
Licence
License this image for commercial use at Science and Society Picture Library
LicenseThis image is released under a CC BY-NC-SA 4.0
Licence
License this image for commercial use at Science and Society Picture Library
LicenseThis image is released under a CC BY-NC-SA 4.0
Licence
License this image for commercial use at Science and Society Picture Library
LicenseThis image is released under a CC BY-NC-SA 4.0
Licence
License this image for commercial use at Science and Society Picture Library
LicenseThis image is released under a CC BY-NC-SA 4.0
Licence
License this image for commercial use at Science and Society Picture Library
LicenseThis image is released under a CC BY-NC-SA 4.0
Licence
License this image for commercial use at Science and Society Picture Library
LicenseThis image is released under a CC BY-NC-SA 4.0
Licence
License this image for commercial use at Science and Society Picture Library
LicenseThis image is released under a CC BY-NC-SA 4.0
Licence
License this image for commercial use at Science and Society Picture Library
LicenseThis image is released under a CC BY-NC-SA 4.0
Licence
License this image for commercial use at Science and Society Picture Library
LicenseThis image is released under a CC BY-NC-SA 4.0
Licence
License this image for commercial use at Science and Society Picture Library
LicenseThis image is released under a CC BY-NC-SA 4.0
Licence
License this image for commercial use at Science and Society Picture Library
LicenseThis image is released under a CC BY-NC-SA 4.0
Licence
License this image for commercial use at Science and Society Picture Library
LicenseThis image is released under a CC BY-NC-SA 4.0
Licence
License this image for commercial use at Science and Society Picture Library
LicenseThis image is released under a CC BY-NC-SA 4.0
Licence
License this image for commercial use at Science and Society Picture Library
LicenseThis image is released under a CC BY-NC-SA 4.0
Licence
License this image for commercial use at Science and Society Picture Library
LicenseThis image is released under a CC BY-NC-SA 4.0
Licence
License this image for commercial use at Science and Society Picture Library
LicenseThis image is released under a CC BY-NC-SA 4.0
Licence
License this image for commercial use at Science and Society Picture Library
LicenseThis image is released under a CC BY-NC-SA 4.0
Licence
License this image for commercial use at Science and Society Picture Library
LicenseThis image is released under a CC BY-NC-SA 4.0
Licence
License this image for commercial use at Science and Society Picture Library
LicenseThis image is released under a CC BY-NC-SA 4.0
Licence
License this image for commercial use at Science and Society Picture Library
LicenseThis image is released under a CC BY-NC-SA 4.0
Licence
License this image for commercial use at Science and Society Picture Library
LicenseThis image is released under a CC BY-NC-SA 4.0
Licence
License this image for commercial use at Science and Society Picture Library
LicenseThis image is released under a CC BY-NC-SA 4.0
Licence
License this image for commercial use at Science and Society Picture Library
LicenseThis image is released under a CC BY-NC-SA 4.0
Licence
License this image for commercial use at Science and Society Picture Library
LicenseThis image is released under a CC BY-NC-SA 4.0
Licence
License this image for commercial use at Science and Society Picture Library
LicenseThis image is released under a CC BY-NC-SA 4.0
Licence
License this image for commercial use at Science and Society Picture Library
LicenseThis image is released under a CC BY-NC-SA 4.0
Licence
License this image for commercial use at Science and Society Picture Library
LicenseThis image is released under a CC BY-NC-SA 4.0
Licence
License this image for commercial use at Science and Society Picture Library
LicenseThis image is released under a CC BY-NC-SA 4.0
Licence
License this image for commercial use at Science and Society Picture Library
LicenseThis image is released under a CC BY-NC-SA 4.0
Licence
License this image for commercial use at Science and Society Picture Library
LicenseThis image is released under a CC BY-NC-SA 4.0
Licence
License this image for commercial use at Science and Society Picture Library
LicenseThis image is released under a CC BY-NC-SA 4.0
Licence
License this image for commercial use at Science and Society Picture Library
LicenseThis image is released under a CC BY-NC-SA 4.0
Licence
License this image for commercial use at Science and Society Picture Library
LicenseThis image is released under a CC BY-NC-SA 4.0
Licence
License this image for commercial use at Science and Society Picture Library
LicenseThis image is released under a CC BY-NC-SA 4.0
Licence
License this image for commercial use at Science and Society Picture Library
LicenseThis image is released under a CC BY-NC-SA 4.0
Licence
License this image for commercial use at Science and Society Picture Library
LicenseThis image is released under a CC BY-NC-SA 4.0
Licence
License this image for commercial use at Science and Society Picture Library
LicenseThis image is released under a CC BY-NC-SA 4.0
Licence
License this image for commercial use at Science and Society Picture Library
LicenseThis image is released under a CC BY-NC-SA 4.0
Licence
License this image for commercial use at Science and Society Picture Library
LicenseThis image is released under a CC BY-NC-SA 4.0
Licence
License this image for commercial use at Science and Society Picture Library
LicenseThis image is released under a CC BY-NC-SA 4.0
Licence
License this image for commercial use at Science and Society Picture Library
LicenseThis image is released under a CC BY-NC-SA 4.0
Licence
License this image for commercial use at Science and Society Picture Library
LicenseThis image is released under a CC BY-NC-SA 4.0
Licence
License this image for commercial use at Science and Society Picture Library
LicenseThis image is released under a CC BY-NC-SA 4.0
Licence
License this image for commercial use at Science and Society Picture Library
LicenseThis image is released under a CC BY-NC-SA 4.0
Licence
License this image for commercial use at Science and Society Picture Library
LicenseThis image is released under a CC BY-NC-SA 4.0
Licence
License this image for commercial use at Science and Society Picture Library
LicenseThis image is released under a CC BY-NC-SA 4.0
Licence
License this image for commercial use at Science and Society Picture Library
LicenseThis image is released under a CC BY-NC-SA 4.0
Licence
License this image for commercial use at Science and Society Picture Library
LicenseThis image is released under a CC BY-NC-SA 4.0
Licence
License this image for commercial use at Science and Society Picture Library
LicenseThis image is released under a CC BY-NC-SA 4.0
Licence
License this image for commercial use at Science and Society Picture Library
LicenseThis image is released under a CC BY-NC-SA 4.0
Licence
License this image for commercial use at Science and Society Picture Library
LicenseThis image is released under a CC BY-NC-SA 4.0
Licence
License this image for commercial use at Science and Society Picture Library
LicenseThis image is released under a CC BY-NC-SA 4.0
Licence
License this image for commercial use at Science and Society Picture Library
LicenseThis image is released under a CC BY-NC-SA 4.0
Licence
License this image for commercial use at Science and Society Picture Library
LicenseThis image is released under a CC BY-NC-SA 4.0
Licence
License this image for commercial use at Science and Society Picture Library
LicenseThis image is released under a CC BY-NC-SA 4.0
Licence
License this image for commercial use at Science and Society Picture Library
LicenseThis image is released under a CC BY-NC-SA 4.0
Licence
License this image for commercial use at Science and Society Picture Library
LicenseThis image is released under a CC BY-NC-SA 4.0
Licence
License this image for commercial use at Science and Society Picture Library
LicenseThis image is released under a CC BY-NC-SA 4.0
Licence
License this image for commercial use at Science and Society Picture Library
LicenseThis image is released under a CC BY-NC-SA 4.0
Licence
License this image for commercial use at Science and Society Picture Library
LicenseThis image is released under a CC BY-NC-SA 4.0
Licence
License this image for commercial use at Science and Society Picture Library
LicenseThis image is released under a CC BY-NC-SA 4.0
Licence
License this image for commercial use at Science and Society Picture Library
LicenseThis image is released under a CC BY-NC-SA 4.0
Licence
License this image for commercial use at Science and Society Picture Library
LicenseThis image is released under a CC BY-NC-SA 4.0
Licence
License this image for commercial use at Science and Society Picture Library
LicenseThis image is released under a CC BY-NC-SA 4.0
Licence
License this image for commercial use at Science and Society Picture Library
LicenseThis image is released under a CC BY-NC-SA 4.0
Licence
License this image for commercial use at Science and Society Picture Library
LicenseThis image is released under a CC BY-NC-SA 4.0
Licence
License this image for commercial use at Science and Society Picture Library
LicenseThis image is released under a CC BY-NC-SA 4.0
Licence
License this image for commercial use at Science and Society Picture Library
LicenseThis image is released under a CC BY-NC-SA 4.0
Licence
License this image for commercial use at Science and Society Picture Library
LicenseThis image is released under a CC BY-NC-SA 4.0
Licence
License this image for commercial use at Science and Society Picture Library
LicenseThis image is released under a CC BY-NC-SA 4.0
Licence
License this image for commercial use at Science and Society Picture Library
LicenseThis image is released under a CC BY-NC-SA 4.0
Licence
License this image for commercial use at Science and Society Picture Library
LicenseThis image is released under a CC BY-NC-SA 4.0
Licence
License this image for commercial use at Science and Society Picture Library
LicenseThis image is released under a CC BY-NC-SA 4.0
Licence
License this image for commercial use at Science and Society Picture Library
LicenseThis image is released under a CC BY-NC-SA 4.0
Licence
License this image for commercial use at Science and Society Picture Library
LicenseThis image is released under a CC BY-NC-SA 4.0
Licence
License this image for commercial use at Science and Society Picture Library
LicenseThis image is released under a CC BY-NC-SA 4.0
Licence
License this image for commercial use at Science and Society Picture Library
LicenseThis image is released under a CC BY-NC-SA 4.0
Licence
License this image for commercial use at Science and Society Picture Library
LicenseThis image is released under a CC BY-NC-SA 4.0
Licence
License this image for commercial use at Science and Society Picture Library
LicenseThis image is released under a CC BY-NC-SA 4.0
Licence
License this image for commercial use at Science and Society Picture Library
LicenseThis image is released under a CC BY-NC-SA 4.0
Licence
License this image for commercial use at Science and Society Picture Library
LicenseThis image is released under a CC BY-NC-SA 4.0
Licence
License this image for commercial use at Science and Society Picture Library
LicenseThis image is released under a CC BY-NC-SA 4.0
Licence
License this image for commercial use at Science and Society Picture Library
LicenseThis image is released under a CC BY-NC-SA 4.0
Licence
License this image for commercial use at Science and Society Picture Library
LicenseGas holder used as a meter and engine testing device
Science Museum Group Collection
© The Board of Trustees of the Science Museum
Gas holder move by National Gas into Gas Gallery.
Science Museum Group Collection
© The Board of Trustees of the Science Museum
Gas holder move by National Gas into Gas Gallery.
Science Museum Group Collection
© The Board of Trustees of the Science Museum
Gas holder used as a meter and engine testing device
Science Museum Group Collection
© The Board of Trustees of the Science Museum
Gas holder used as a meter and engine testing device
Science Museum Group Collection
© The Board of Trustees of the Science Museum
Gas holder move by National Gas into Gas Gallery.
Science Museum Group Collection
© The Board of Trustees of the Science Museum
Gas holder move by National Gas into Gas Gallery.
Science Museum Group Collection
© The Board of Trustees of the Science Museum
Gas holder used as a meter and engine testing device
Science Museum Group Collection
© The Board of Trustees of the Science Museum
Gas holder move by National Gas into Gas Gallery.
Science Museum Group Collection
© The Board of Trustees of the Science Museum
Gas holder move by National Gas into Gas Gallery.
Science Museum Group Collection
© The Board of Trustees of the Science Museum
Gas holder move by National Gas into Gas Gallery.
Science Museum Group Collection
© The Board of Trustees of the Science Museum
Gas holder used as a meter and engine testing device
Science Museum Group Collection
© The Board of Trustees of the Science Museum
Gas holder move by National Gas into Gas Gallery.
Science Museum Group Collection
© The Board of Trustees of the Science Museum
Gas holder move by National Gas into Gas Gallery.
Science Museum Group Collection
© The Board of Trustees of the Science Museum
Gas holder move by National Gas into Gas Gallery.
Science Museum Group Collection
© The Board of Trustees of the Science Museum
Gas holder used as a meter and engine testing device
Science Museum Group Collection
© The Board of Trustees of the Science Museum
Gas holder used as a meter and engine testing device
Science Museum Group Collection
© The Board of Trustees of the Science Museum
Gas holder move by National Gas into Gas Gallery.
Science Museum Group Collection
© The Board of Trustees of the Science Museum
Gas holder used as a meter and engine testing device
Science Museum Group Collection
© The Board of Trustees of the Science Museum
Gas holder used as a meter and engine testing device
Science Museum Group Collection
© The Board of Trustees of the Science Museum
Gas holder used as a meter and engine testing device
Science Museum Group Collection
© The Board of Trustees of the Science Museum
Gas holder used as a meter and engine testing device
Science Museum Group Collection
© The Board of Trustees of the Science Museum
Gas holder used as a meter and engine testing device
Science Museum Group Collection
© The Board of Trustees of the Science Museum
Gas holder move by National Gas into Gas Gallery.
Science Museum Group Collection
© The Board of Trustees of the Science Museum
Gas holder move by National Gas into Gas Gallery.
Science Museum Group Collection
© The Board of Trustees of the Science Museum
Gas holder move by National Gas into Gas Gallery.
Science Museum Group Collection
© The Board of Trustees of the Science Museum
Gas holder move by National Gas into Gas Gallery.
Science Museum Group Collection
© The Board of Trustees of the Science Museum
Gas holder move by National Gas into Gas Gallery.
Science Museum Group Collection
© The Board of Trustees of the Science Museum
Gas holder move by National Gas into Gas Gallery.
Science Museum Group Collection
© The Board of Trustees of the Science Museum
Gas holder move by National Gas into Gas Gallery.
Science Museum Group Collection
© The Board of Trustees of the Science Museum
Gas holder move by National Gas into Gas Gallery.
Science Museum Group Collection
© The Board of Trustees of the Science Museum
Gas holder move by National Gas into Gas Gallery.
Science Museum Group Collection
© The Board of Trustees of the Science Museum
Gas holder move by National Gas into Gas Gallery.
Science Museum Group Collection
© The Board of Trustees of the Science Museum
Gas holder move by National Gas into Gas Gallery.
Science Museum Group Collection
© The Board of Trustees of the Science Museum
Gas holder move by National Gas into Gas Gallery.
Science Museum Group Collection
© The Board of Trustees of the Science Museum
Gas holder move by National Gas into Gas Gallery.
Science Museum Group Collection
© The Board of Trustees of the Science Museum
Gas holder move by National Gas into Gas Gallery.
Science Museum Group Collection
© The Board of Trustees of the Science Museum
Gas holder move by National Gas into Gas Gallery.
Science Museum Group Collection
© The Board of Trustees of the Science Museum
Gas holder move by National Gas into Gas Gallery.
Science Museum Group Collection
© The Board of Trustees of the Science Museum
Gas holder move by National Gas into Gas Gallery.
Science Museum Group Collection
© The Board of Trustees of the Science Museum
Gas holder move by National Gas into Gas Gallery.
Science Museum Group Collection
© The Board of Trustees of the Science Museum
Gas holder move by National Gas into Gas Gallery.
Science Museum Group Collection
© The Board of Trustees of the Science Museum
Gas holder move by National Gas into Gas Gallery.
Science Museum Group Collection
© The Board of Trustees of the Science Museum
Gas holder move by National Gas into Gas Gallery.
Science Museum Group Collection
© The Board of Trustees of the Science Museum
Gas holder move by National Gas into Gas Gallery.
Science Museum Group Collection
© The Board of Trustees of the Science Museum
Gas holder move by National Gas into Gas Gallery.
Science Museum Group Collection
© The Board of Trustees of the Science Museum
Gas holder move by National Gas into Gas Gallery.
Science Museum Group Collection
© The Board of Trustees of the Science Museum
Gas holder move by National Gas into Gas Gallery.
Science Museum Group Collection
© The Board of Trustees of the Science Museum
Gas holder move by National Gas into Gas Gallery.
Science Museum Group Collection
© The Board of Trustees of the Science Museum
Gas holder move by National Gas into Gas Gallery.
Science Museum Group Collection
© The Board of Trustees of the Science Museum
Gas holder move by National Gas into Gas Gallery.
Science Museum Group Collection
© The Board of Trustees of the Science Museum
Gas holder move by National Gas into Gas Gallery.
Science Museum Group Collection
© The Board of Trustees of the Science Museum
Gas holder move by National Gas into Gas Gallery.
Science Museum Group Collection
© The Board of Trustees of the Science Museum
Gas holder move by National Gas into Gas Gallery.
Science Museum Group Collection
© The Board of Trustees of the Science Museum
Gas holder move by National Gas into Gas Gallery.
Science Museum Group Collection
© The Board of Trustees of the Science Museum
Gas holder move by National Gas into Gas Gallery.
Science Museum Group Collection
© The Board of Trustees of the Science Museum
Gas holder move by National Gas into Gas Gallery.
Science Museum Group Collection
© The Board of Trustees of the Science Museum
Gas holder move by National Gas into Gas Gallery.
Science Museum Group Collection
© The Board of Trustees of the Science Museum
Gas holder move by National Gas into Gas Gallery.
Science Museum Group Collection
© The Board of Trustees of the Science Museum
Gas holder move by National Gas into Gas Gallery.
Science Museum Group Collection
© The Board of Trustees of the Science Museum
Gas holder move by National Gas into Gas Gallery.
Science Museum Group Collection
© The Board of Trustees of the Science Museum
Gas holder move by National Gas into Gas Gallery.
Science Museum Group Collection
© The Board of Trustees of the Science Museum
Gas holder move by National Gas into Gas Gallery.
Science Museum Group Collection
© The Board of Trustees of the Science Museum
Gas holder move by National Gas into Gas Gallery.
Science Museum Group Collection
© The Board of Trustees of the Science Museum
Gas holder move by National Gas into Gas Gallery.
Science Museum Group Collection
© The Board of Trustees of the Science Museum
Gas holder move by National Gas into Gas Gallery.
Science Museum Group Collection
© The Board of Trustees of the Science Museum
Gas holder move by National Gas into Gas Gallery.
Science Museum Group Collection
© The Board of Trustees of the Science Museum
Gas holder move by National Gas into Gas Gallery.
Science Museum Group Collection
© The Board of Trustees of the Science Museum
Gas holder move by National Gas into Gas Gallery.
Science Museum Group Collection
© The Board of Trustees of the Science Museum
Gas holder move by National Gas into Gas Gallery.
Science Museum Group Collection
© The Board of Trustees of the Science Museum
Gas holder move by National Gas into Gas Gallery.
Science Museum Group Collection
© The Board of Trustees of the Science Museum
Gas holder move by National Gas into Gas Gallery.
Science Museum Group Collection
© The Board of Trustees of the Science Museum
Gas holder move by National Gas into Gas Gallery.
Science Museum Group Collection
© The Board of Trustees of the Science Museum
Gas holder move by National Gas into Gas Gallery.
Science Museum Group Collection
© The Board of Trustees of the Science Museum
Gas holder move by National Gas into Gas Gallery.
Science Museum Group Collection
© The Board of Trustees of the Science Museum
Gas holder move by National Gas into Gas Gallery.
Science Museum Group Collection
© The Board of Trustees of the Science Museum
Gas holder move by National Gas into Gas Gallery.
Science Museum Group Collection
© The Board of Trustees of the Science Museum
Gas holder move by National Gas into Gas Gallery.
Science Museum Group Collection
© The Board of Trustees of the Science Museum
Gas holder move by National Gas into Gas Gallery.
Science Museum Group Collection
© The Board of Trustees of the Science Museum
Gas holder move by National Gas into Gas Gallery.
Science Museum Group Collection
© The Board of Trustees of the Science Museum
Gas holder move by National Gas into Gas Gallery.
Science Museum Group Collection
© The Board of Trustees of the Science Museum
Gas holder move by National Gas into Gas Gallery.
Science Museum Group Collection
© The Board of Trustees of the Science Museum
Gas holder move by National Gas into Gas Gallery.
Science Museum Group Collection
© The Board of Trustees of the Science Museum
Gas holder move by National Gas into Gas Gallery.
Science Museum Group Collection
© The Board of Trustees of the Science Museum
Gas holder move by National Gas into Gas Gallery.
Science Museum Group Collection
© The Board of Trustees of the Science Museum
Gas holder move by National Gas into Gas Gallery.
Science Museum Group Collection
© The Board of Trustees of the Science Museum
Gas holder move by National Gas into Gas Gallery.
Science Museum Group Collection
© The Board of Trustees of the Science Museum
Gas holder move by National Gas into Gas Gallery.
Science Museum Group Collection
© The Board of Trustees of the Science Museum
Gas holder move by National Gas into Gas Gallery.
Science Museum Group Collection
© The Board of Trustees of the Science Museum
Gas holder move by National Gas into Gas Gallery.
Science Museum Group Collection
© The Board of Trustees of the Science Museum
Gas holder move by National Gas into Gas Gallery.
Science Museum Group Collection
© The Board of Trustees of the Science Museum
Gas holder move by National Gas into Gas Gallery.
Science Museum Group Collection
© The Board of Trustees of the Science Museum
Gas holder move by National Gas into Gas Gallery.
Science Museum Group Collection
© The Board of Trustees of the Science Museum
Gas holder move by National Gas into Gas Gallery.
Science Museum Group Collection
© The Board of Trustees of the Science Museum
Gas holder move by National Gas into Gas Gallery.
Science Museum Group Collection
© The Board of Trustees of the Science Museum
Gas holder move by National Gas into Gas Gallery.
Science Museum Group Collection
© The Board of Trustees of the Science Museum
Gas holder move by National Gas into Gas Gallery.
Science Museum Group Collection
© The Board of Trustees of the Science Museum
Gas holder move by National Gas into Gas Gallery.
Science Museum Group Collection
© The Board of Trustees of the Science Museum
Gas holder move by National Gas into Gas Gallery.
Science Museum Group Collection
© The Board of Trustees of the Science Museum
Gas holder used as a meter and engine testing device, traditionally known as a 'gasometer'. For use in accurate volumetric town gas measurement, typically in gas supply meter calibration. Made by Parkinson & WB Cowan Ltd in 1923, and used by Perkins
Engine Co Ltd until 2010 as an engine flow-meter calibrator and called by them a 'bell prover'.
Hollow cast iron cylinder with moving bell within, the whole surmounted by twin columns and associated counterweight and valve gear to one side and face.
Parts of a gas holder used as a meter and engine testing device, traditionally known as a 'gasometer'. Made by Parkinson & WB Cowan Ltd in 1923, and used by Perkins Engine Co Ltd until 2010 as an engine flow-meter calibrator and called by them a 'bell prover'.
Gas holder meter tester base section; cylindrical with boiler inside a casing. Also has two rods and the two twin columns.
Made by Parkinson & WB Cowan Ltd in 1923, and used by Perkins
Engine Co Ltd until 2010 as an engine flow-meter calibrator and called by them a 'bell prover'.
Gas holder meter tester top section; upper beam, with wheels, dial hand, rope with weights attached and steel rope.
Made by Parkinson & WB Cowan Ltd in 1923, and used by Perkins
Engine Co Ltd until 2010 as an engine flow-meter calibrator and called by them a 'bell prover'.
