An extremely rare and little-documented prototype zoom lens developed by GOI (State Optical Institute) for the Almaz K-mount SLR system, produced in a very small experimental batch in the late 1970s.Designated Jantar-17, the lens covers 35–70mm with a variable aperture of f/2.8–3.7, representing an early Soviet attempt at a fast standard zoom for 35mm cameras. Finished in characteristic black paint typical of late GOI prototypes, with hand-finished details and non-standard engravings. In fine condition, with good optics and functional mechanics.A highly interesting and rare example of Soviet prototype lens development for the Almaz system. SN: 86207