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 adapters. The second unit was given to me by Vince Celano who got it in about 1965 from Jack Lowther, a relative by marriage. He lived in St Annes on Sea and dabbled a bit with things electrical. Vince didn't use it that much as being a young lad building lots of stuff he bought mainly new valves as his dad helped buy the valves when he had nearly finished building the chassis of whatever it was.
As received the first unit 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 key switch, I made a tool from a piece of thin steel wire and managed to bend the offending switch contact so that it made contact when the key was in the "off" position. I did however remove the meter movement and clean the dial and glass. The connecting lead has been replaced and a new mains lead has been fitted. An additional £ 3 sent to firstname.lastname@example.org provided me with a set of operating instructions and a very useful set of schematic diagrams.
As received the second unit was also quite grubby, the meter pointer was bent, three of the switch knobs had been replaced and the select anode switch did not work correctly and the neon indicator had failed. I removed the meter movement, straightened the pointer and cleaned the dial and glass. Vinc also gave me a 1965 letter from AVO and two blueprint schematic diagrams.
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 top caps 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. The Admiralty unit was made in May 1946 and the other in April of the same year. See advert (date unknown) below for original cost and details:
What is it worth today? for a working instrument in good condition you might reasonably expect to get between £ 70 and £ 75. The inclusion of a manual would increase the value.