serial number 297210
This model, made for the British Post
Office, is a variation of the model 73A which is an updated more versatile
better protected version of the earlier model 71 and model 72. The basic construction and circuitry
is much the same but the meter movement is protected by a
number of small neon tubes and a 3.15A fuse which has a neon and
resistor connected across it to indicate failure. The versatile
moulding for the meter and batteries has holes for additional sockets
so that it can be used for the other meters in the range.
Unlike other instruments I have seen in this range, the printed circuit and components are shrouded with a white plastic cover which I have not removed. I assume the internals are as shown on another model PO 12D included on this page which describes these instruments and other similar models. AVO produced a range of the smaller multimeters which are described here
I was given this meter by Johannes Allart who was having a clear out and said I could have it as long as I paid the postage. When I arrived it proved to be in working order although the battery clips showed signs of corrosion and needed to be cleaned. The substantial leather case, as he had intimated, had a musty smell and needed a good clean and a couple of applications of leather polish. The rusty steel rivets buckle and screws were cleaned up using my Dremel with a small grindstone. I was intrigued by the label and Johannes told me that the meter had originally belonged to his neighbour, Dennis Miller who was from Bournemouth and used it to check washing machines. The premises still exist selling second hand goods.
How much is it worth? Instruments such as this are of little use today and not many people seem interested in them. Expect to pay £10-£15.