Gunter sector made by John Allen in 1623, Strand, London. It is signed 'John Allen fecit'.
Sectors are mathematical instruments that were used for calculations concerning proportion and for making small measurments. They were particularly useful for technical drawing. This example contains logarithmic and trigonometric lines and scales used in drawing and calculations of area and volume. John Allen (active 1630-42) was a mathematical instrument maker who was apprenticed to Elias Allen and became a Freeman in both the Grocers' and Clockmakers' Companies. His workshop was locatred on the Strand in London.