The above pictures are of an early model two panel Valve Tester which I purchased on eBay. This is an Admiralty pattern 55046 model with cutout indicator. Luckily it included an "AVO Valve Data Manual" 17th edition 1965 together with several additional valve base adaptors.
As received it was very dirty and the interior of the socket panel was rusty, the key switch did not work correctly and the contact switch on the insulation test socket was not making connection. Rather than taking the whole tester apart to get at the keyswitch, I made a tool fom a piece of thin steel wire and managed to bend the offending switch contact so that it made contact when the ke was in the "off" position. I did however remove the meter movement and clean the dial and glass. An additional £ 3 sent to sales@crowthornetubes.com provided me with a set of operating instructions and a very useful set of schematic diagrams.
The connecting lead has been replaced and a new mains lead has been fitted. The panel has 15 sockets of various types and provision to add others. Easy to use by dialling the roller switches which are numbered to correspond to the standard numbering used by all valve manufacturers. Valves with topcaps are connected by a flying lead to sockets A,G or S.
The original AVO two panel valve tester was introduced in 1936 and with minor modifications remained much the same for many years. I guess that my unit was made in the late 1940's. See advert (date unknown) below for original cost and details:
