Leitz Elmar 2.8/5cm M39 A36 prototype

A very rare and interesting transitional M39 lens merging the features of the f:3.5 Elmar and the production f.2.8 version, the barrel and the top of the lens are already very similar to the production lens (albeit in A36 size), the focusing mount is similar to the f.3.5 Elmar, with slight mechanical differences and additional engravings on the depth-of-field scale.

Photo credit: © Leitz Photographica Auction