Electroflo Smoke Density Meter
Electroflo smoke density meter [remainder at Blythe House]
Electroflo smoke density meter (in parts for a demonstration)
Electroflo smoke density meter [remainder at Blythe House]
Part of Electroflo smoke density meter, hand which has a metal rod protruding from the top.
A chart, part of Electroflo smoke density meter. A standard Ringelmann chart.
"These grids are a direct facsimile reduction of the standard Ringelmann Chart as issued by the United States Bureau of Mines. Copyright 1954 by McGraw-Hill Publishing Company, Inc. (Publisher of Power) 330 W 42nd St, New York 36 N Y. Price. 35c each, discount on quantities."