Treading dangerous ground...Kids, don't try this at home!
Just to prove it can be done...
Conventional wisdom is that the LZOS Jupiter-12 35/2.8 whether adapted or native mount is not compatible with Bessa rangefinders. I have no doubt that such is commonly true for most versions of said lens and said cameras and even a few issued by the makers of adapters. Amadeo says do not do for the adapter pictured in the photo above.
I took this advice strongly at face value until it was suggested to me that it might not be true (thank you Colton Allen). Sure enough, my late production Bessa R3M has cut-out's in the light baffles, top and bottom, that appeared adequate for clearance. A little careful testing in "B" mode proved this to be true, hence this photo. Note that there may still be an issue with earlier production Jupiter-12 and particularly with the Biogon 35mm since that lens has a protective collar around the rear element. There may also still be problems with other Voigtländer models. Test before jamming a lens into that opening. YMMV.
I might also note that the bulbous rear on the lens obscures the meter cell, so no TTL metering with this one mounted. FWIW, my LTM copy also fits.
So that all is clear...
Bessa R3M, sn 0002025
LZOS Jupiter-12 35/2.8 (Contax/Kiev), sn 8006281
LZOS Jupiter-23 35/2.8 (LTM), sn 8206732
When mounting, set lens to to minimum focus distance. Likewise, it is preferable to set to MFD before attempting removal. Clearance is very tight to the top and bottom molding at infinity. I don't think I would recommend this combination for general shooting.