Unidentified thread-adapter

[MichaelG.]

A hopefully trivial question, to which someone might give me an instant answer:

I am in the process of cataloguing my modest collection of adapters, and came across this one
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IMG_9342.jpeg (161.19 KiB) Viewed 160 times

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The nicely baffled interior may be a clue, and the number 520544 has a Zeiss look to it

Female thread is M42 but the male is unusual in being 33mm



Thanks for any assistance with identification

MichaelG.
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Edit: just discovered that some Rodenstock enlarging lenses use 33mm

[PeteM]

No idea what it fits. However, the 520544 number could well be a Leitz/early Leica identification. Later ones, in microscope accessories, will have a "10" in front (e.g. 10520544).

The M42 end would be useful, even if you ended up adapting something else to the small end.

[MichaelG.]

Thanks for that, PeteM
… looks like we’re homing-in on Germany

MichaelG.