This Zenit-E has a plate attached to the back cover that reads:
On your 18th birthday
From Mama, Papa and Sergey. 24/08/83.
I would like to point that this camera made in 1968 but it was presented as a birthday gift 15 year later, in 1983. To me this tells a lot about life in Soviet Union at that time. Camera most likely was in a family as a prize possession. It may rarely be used and kept in pristine conditions by old generation.
It was giving to next generation as a present not just for any birthday, but for a biggest birthday – 18th birthday. The day when person legally became full-blown USSR citizen, able to vote, buy liker, married, serve as elected official, and be fully responsible for his/her deeds before low. For most man it also means time to go to army, and be away from home first time in his live.
So this Zenit was giving most likely as a greatest and possibly the only present from closest family to the teenager who just became an adult.
Pretty interesting find!