Irwin dynomometer wattmeter, in mahogany carrying case
Irwin dynomometer wattmeter by the Cambridge Instrument Co. Ltd. No. L 24972
Irwin dynomometer wattmeter by the Cambridge Instrument Co. Ltd. No. L 24972, with accompanying documentary material
Irwin dynomometer wattmeter by the Cambridge Instrument Co. Ltd. No. L 24972
Documentary material for Irwin dynomometer wattmeter by the Cambridge Instrument Co. Ltd. No. L 24972