The Talking Machine Forum — For All Antique Phonographs & Recordings

From the front this soundbox, which sold recently on eBay with a number of HMV102 components, looks like a 5B.
Turn it over and "5AB" is clearly stamped on the backplate. I have never seen this before. Has anyone else?

Personally, first time that I see one or that I read it mentioned. Interesting.

Something tells me we need "Oedipus" for possibly solving this one...

I have never seen this before.

I assume that the 'marks' were usually stamped by machine (and not by hand) and that the lettering / numbers are the same size 'as usual' ?

Very interesting indeed.

I don't think these markings are 'stamped', but rather are in the die from which the backplate is cast. That means that there must be others with this peculiar marking, but I have never seen it, either. Possibly this is an early 5B, and the die was incorrectly marked with an added 'B' rather than a substituted one. Or it could have been deliberate, so that the backplate could have been used either for a 5A or a 5B during the transition. But that is speculation, and I don't know the answer!

In the few examples I do have, the 5a and 5b parts are interchangeable, and the only difference I've found are the diaphragm edge corrugations, and four special legs punched in the metal cover beside the four screws, as made to avoid the cover being pressed too deep on the front ring because of tight screwing. This example has both features.

is it possible that in the last years of production only one spare reproducer was available and this was designated AB as a universal replacement for either A or B reproducer?

I'm just waiting to find an "ABC" variant. Now, that would blow a few minds here!

No, I've never seen AB either. It must be extremely rare. I agree with Oedipus though. It might only be guesswork but it's as good a guess as any.