The reverse of the card reads: 'Fixing the Tuning Condenser. The variable condenser is an "Ormond" .0005 micro farad S L F No 3 and is fitted into the 3/8-inch hole nearest to the left of the panel when viewed from the front. The fixing is the well-known "one-hole" method, the instrument being held in place by a single nut, which is secured firmly by means of a suitable spanner. Care should be taken when handling to avoid bending or damaging the thin vanes. The slow motion dial is also shown on the front of the bench.'
© Science Museum / Science & Society Picture Library