'How to build a two valve set', No 5, Godfrey Philips cigarette card, 1925.
© Science Museum / Science & Society Picture Library
The reverse of the card reads: 'Fixing slow motion dial. This picture shows how the 'Ormond' slow motion dual indicator dial is fixed. A coin is used to tighten the dial on the condenser spindle. Full printed instructions are isued with the dial when sold.'