odd 1930ies COMPUR shutter replacement?

I have a Zeiss Jena lens here mounted in a COMPUR shutter (which I need to
replace) and the sizes of the lens elements are strange for me (M36 x 0.75
on front AND rear) - unknown to me! Usually this was for a size I
shutter M40 x 0.75 (front) and M36 x 0.75 (rear) and for a size O
M29.5 x 0.75 (front + rear). The age of my lens is about 1930 I would
say, so which COMPUR type is that and where could I find a
replacement or a barrel w. iris I could mount the lens elements into?

Enlighten me please!!

Thanks, Klaus
postmaster@macrolenses.de

KLaus, It might help to know which lens:
eg., Convertible Protars have same front and rear threads.
Good Luck,
Bernie

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