According to this web page on the Schneider site, this lens was made sometime after November 1951, and before May 1952. A real antique!
It has a preset diaphragm, lots and lots of diaphragm blades (like the Russian lenses), and the (uncoated) front element is deeply set and so a hood is probably not needed.
It was in Exakta mount, but I did a temporary work-around by wrapping snippets of business card around the Exakta bayonet and then push-fitting an M42-Pentax K adapter ring over the business cards:
Wobbly, and it doesn't quite reach infinity focus.
From the performance of this lens, it is an uncoated triplet, very much like the Zeiss Triotar. It has low contrast wide-open, and is not as sharp as its East German sibling, the Zeiss Jena 135mm f/3.5 Sonnar.
|Zeiss Sonnar||Schneider Xenar|
Probably interesting for portraits and I'm eager to see its bokeh. I assume the bokeh is very nice, given the circular diaphragm opening.
I had some high hopes for "retro photography" with this lens, but bad luck reared its ugly head. While I was fiddling with it today, the front element fell out (my fault) and gained a large edge chip (a more accurate way of saying that is, "Orly unscrewed the front retaining ring, turned the lens over to look at something inside, and the front element fell on the floor and a piece of its edge got broken").
Technical me knows that such a chip (I even blackened it for good measure) has no effect on the photos, but that chip just reduced the lens' resale value by a huge amount. Not that I'm complaining, having gotten it for $9.00 - but it really was worth around $80 (I just got lucky on the bid), and I was hoping to build up a collection of antique lenses for future generations.