This is a factory Grey covering version of Zorki S camera. These are known to be made from 1956 to 1958.
The Zorki-C(S) has a taller finder to accomodate the flash sychronizer. The rewind switch is now a collar around the shutter release instead of a seperate lever. It doesn't have a self-timer. Some of camera bodies are covered with ribbed nylon instead of vulcanite and come in several colors.
Produced: 1955-1958
Name: „Зоркий-C“
Producer: KMZ
Frame size: 24x36.
Lens: Industar-22 3.5/50.
Shutter: 1/25s, 1/50s, 1/100s, 1/250s, 1/500s + B.
Quantity: 472.702 units.
Source: www.sovietcams.com
An excellent classificator for the Zorki-C series can be found at:
http://www.sovietcams.com/index.php?542408128
Image #4 is a variation without the "Made in USSR" inscription on the back (Courtesy of Michel Chretien)