I like the 3133 and 31681 (they're the same, except the 3133 doesn't have the 24h sub dial). And yes, they are extremely similar to a Valjoux 7734. The original tooling for the 3133 was bought by the USSR from Valjoux, so I wouldn't be surprised if some of the parts are still interchangeable. There are a few differences (and the date complication is completely different), but they are close enough that I used a 7734 service manual as a guide when I serviced one of my 3133s: