Wollensak Velostigmat 50mm- what else is there to know?

[ZorkiKat]

In Leica M39 mount. Collapsible like the Elmar...

I know, or believe, that:

...it has the Tessar, rather than the Elmar config, with the aperture blade between the middle and back lens components;

...it was made in the USA for Leitz NY to substitute for the Elmar, to be used on Leica, when the real lenses were impossible to import during WW2...

(or was it not? Did Leitz NY make Wollensak substitutes as alternatives to the real Leitz lenses, with or without the war?)

But, why is this lens marked in metres rather than feet? (See arrow in photo) American photo equipment from the 1940s to 50s, AFAIK were always calibrated in feet. Did Leitz NY export this lens to Europe where the metric scale is appreciated?

Or if it was a wartime substitute, and produced at the time before coating was routine, why does this lens have a blue AR coating?

And, finally, how common or rare is this lens?

I haven't found much about it on the net.

I've shot with it once, and the quality is about the same as the Industar-10 from FED... The Industar-22 appears to do better.

 

[Dwig]

According to both of my references (James Lager's "Illustrated Guide II" and Hove's "Leica Pocket Book") the Velostigmat lenses were post-war, not war time, stand-ins for unavailable Leitz lenses. There were made in 50, 90, and 135mm. Lager states that the 50 f/3.5 was available from early '47 though later '49. The 135 was available as early as '45. The serial numbers don't fall into the Leitz number pattern and can't be used for dating using Leitz number records.

Neither mentions mount calibrations. Lager illustrates two samples of the f/3.5, both marked in ft. Lager also shows two somewhat rare f/2.8 variants which both had mounts marked "Germany", though one lens unit is marked E. Leitz NY. E. Leitz NY may well have made some for export to markets where meter's were preferred, but neither of my sources makes any mention of such.