Last year, I took a chance on a job lot of "camera gear" on the big auction site, which included some Leica stuff. I got a Leica IIIb, 9cm Elmar and universal finder as well as a perfect Weston exposure meter and miscellaneous other photography things.
The gem was the Summar which was just about visible in the listing pictures; it turned out to be an early nickel black-nose version manufactured in 1933. The lens had been well used, and at some point had been coated, but the coating was in poor condition.
However, being coated seemed to have protected the glass from any massive damage, so I had the lens properly restored by Malcolm Taylor, which included removal of the coating to return it to original specification. It now has a nice patina of use, with perfect optics.
Initial photographs were taken on expired Orwo NP55 cine film using my 1935 IIIa body. Probably not the best film to use as a test, but already I can see that the sharpness and contrast are superb.
Taken with a Leica IIIa (1936) and uncoated Summar 5cm f2 (1933) on expired Orwo NP55 cine film processed in Orwo A49 (Agfa Atomal):