All of the Meteor boats with two digits were in service from 60s to 80s, can't see the exact number on this one, probably ends in 2 or 8. According to search for Leningrad in www.spkfleet.ru should be 28 38 or 92. Most likely 38 but specific number doesn't affect dating much anyway.
Early 70s considering the general lack of cars and ZAZ 968 + a possible VAZ 2104 in the other photo on this film. Also one of them shows a Meteor-65, which started operation in 1968 so 70s are most likely.