These cameras were produced by factory "KMZ" (Krasnogorsk) since 1962 up to 1970.
About 781,678 copies were made
Frame size 24X36mm

Lenses(screw mount M39): Industar-50 (3.5/50mm), Helios-44 (2/58mm)

Adjustable shutter speeds - 1/30, 1/60, 1/125, 1/250, 1/500 of a second and "B".

Same camera as Kristall only with classic chrome top. Totally different design from Zenit 3. Camera has open back, lever cocking mechanism, pressure molding casing, redesigned shatter.
All this improvement was necessary to made camera more technological to make and use conveyer to produce 1000th of cameras each month.