it looks like I'm going down the Detective Brettschneider's route, remember this guy from Hasek's Brave Soldier Svejk? He kept buying dogs from Svejk to wheedle out some info from him, and he ended up being eaten with all the pack collected
Today I've got a speckless, perfect specimen of Schneider Xenar 135/4.5 in dial-set Compur (working fine, a small handle on the diaphragm lever down there is broken off - that's nothing). Made around 1929, the glass is perfect - there's not a single scratch. Well, that's the third lens of this class I possess, am I nuts? But that was only $30... would this Xenar be any good, or pictorially different with, say, echt Zeiss Tessar 135/4.5 of the same time?
I have this lens and like it a lot. The only problem for me is that it has a coverage of 160mm, just covers 4X5 without ANY movement. I can't speak to the Tesar but I do not see any reason to replace mine except for the coverage.
I've got one of those too - and a 135/3.5 Xenar Typ D, a 135/4.5 Tessar, a 150/4.5 Xenar (late-ish), a 150/9 G-Claron, a 150/9 Germinar-W, a 150/4.5 Apo-Lanthar, a 150/4.5 Heliar, a 135/4.5 Eurynar - and that's only the ones in working shutters!
I have just dispatched 3 guys..big and burly..along with what I hope is a jacket that will fit you. You should be able to lick this insidious disease..it has been given the name of Oleoldlensdeepfiord syndrome..if you stay away from your computer and do not drink beverages sold by Olaf and James Galli vinters of diffraction.
Zhenya, the next time you feel tempted to buy a lens that's like several you have already, calculate how many ice cream cones you'll have to give up to pay for it. Is the lens worth it? I bet not!
Zhenya, I have no direct experience with Xenar lenses, but I don't find there's a visible difference between my ca. 1935 Skopar 13.5 cm f/4.5 and my pair of ca. 1926 CZJ Tessars of the same specification. I'd have to do side-by-side testing to be certain, but surely there's no difference that would show in, say, an 18x24 cm print from 9x12 cm film...