[pmmunro]

Thanks everyone for your interest.

It might have helped if I'd attached an image so that it's clear which unit I'm referring to as AVO's naming convention and lack of type numbers is a good formula for confusion.

Due to the file size limit here, the image quality is not great but should be enough to show the range of instruments to which this one belongs - it's the same range as the Type 378 signal generator (CT378A) and the Transistor Analyser (Inter Services Spec. K.114).

As the catalogue page shows, "This instrument meets the requirements of the U.K. Air Registration Board" but since that was a civil avaiation authority it doesn't necessarily follow that there was a military version although I thought another forum contributor had written that theirs was a Services version.

As Ed commentated above, it is made to a very high standard and price lists show it cost 3 times a contemporary Model 8 multimeter, so it does seem it might have had to meet an MOD specification.

PS - A higher quality image (Creative Commons licence) courtesy of the Science Museum

PMM