This lens is unusual. Trying to find a pre-war CZJ 5cm F2 Sonnar with clean glass is about like trying to find a Summar with a perfect front element. I have one uncoated F2 Sonnar that is close. But- the F1.5 lenses have simply aged better. I've worked on 15 of them, and the glass always was in better condition than the 15 or so F2 "Little Brothers".
Then- I found this oddball lens on an Ebay auction. Funny engraving, in an M39 non-focusing mount, looks like it was used for an enlarger or "something". $20 and it was mine.
It arrived, SN 170xxxx on the front- ring did not look right. But, the rear group had the right SN's. And all of the surfaces were coated, and near perfect. The Optics Module was correct, but was cemented into the M39 enlarger lens housing. The front element had been removed from its metal stamp, coated, and placed back- somewhat loosely. So I moved all of the glass in their metal stamps into a new optics fixture from a Sonnar with an unusable front element. I used clear nail polish to set the loose front element into the metal stamp.
First quick test: on the Olympus EP2.
100% crop on the EP2
F2, some color, strong backlight.
I'll probably convert this to Leica mount, using a J-8 focus mount. Or- leave on the collapsible mount for the Nikon RF. I shimmed it to focus on the Nikons. Mind is not made up about the final mount, but at least I know what it is like to shoot with a near-perfect prewar F2 Sonnar.