This lens is one of the first Soviet telephoto lenses with an M39 mount, created exclusively as a prototype for the earliest black Fedka cameras. A notable characteristic of this unique lens is the internal focusing design, which is quite uncommon for a pre-war model, allowing it to maintain the same length when focusing. The serial number suggests it was manufactured around 1935, predating the mass production of interchangeable lenses for Fed cameras, which began in other Soviet factories in 1938. The lens is in very good condition and includes an original GOI wooden case with a matching serial number.