'How to build a two valve set', No 8, Godfrey Philips cigarette card, 1925.
© Science Museum / Science & Society Picture Library
The reverse of the card reads: 'Fixing valve holder. The two valve holders are next fixed to the baseboard with ordinary screws - 3/4 in No 6 are suitable. The one being screwed down in the picture should be fixed with its edge 1 inch from the back edge of the baseboard and 1/2 inch from the end. The other one 4 1/2 inches towrds the other end of the baseboard. The positions are more clearly indicated on card No 11. Care must be taken to see that the filament terminals are in line and that the anode terminals are to the left when viewed from the back.'