Model: 4 (YU 11/4 - ю 11/4)
Cell type: Selenium
Measure type: reflecting/averaging; 2D incident with attachment
Russian stuff is notoriously difficult to research. The vast gulf in language and culture is bad enough; add the fact that they were a closed society for decades and publishing their product history was a non-existent priority. Add the fact that even though there were "companies," everything was state-owned and products could be developed here, produced there, and moved here there and elsewhere at the whim of a government beaurocrat who had the power to make it happen for any reason he saw fit. It's tough to learn much about Russian equipment..
To look at it, it appears to be a knock-off of a Gossen Luna-Pro, but the big difference is that the Luna-Pro is CdS, and this still uses a selenium cell. Selenium is great because you don't have to deal with batteries, but its low-light sensitivity is poor and that was one of the Luna-Pro's primary features. But from a sales-gimmick point of view, and I imagine most of these were exported, it does look modern and very 1960s/70s, whereas the earlier Leningrads looked very late-art-deco 1950s. This meter says I am Post-Sputnik.
This is quite a nice meter. It's bright and easy to read. There's a big slide-switch on the side which is the high-low scale switch; it's spring-loaded so you have to hold it to stay in Low, and then it flips back. The meter scale is on a roller so when you go to Low, the scale changes appropriately. Mine still works, though I haven't checked its accuracy.
There is no Leningrad 3, in case you've been looking at the numbering. Or at least, nobody I know has seen a Leningrad 3. My guess is that it was developed but never marketed, or was made in such small numbers that few exist. There are three missing numbers in the Leningrad line: 3, 5 and 9; each missing number occurs when there's a major redesign of the meter.
Here is a cross-reference chart for film speeds (ASA / ISO / DIN / GOST / others) .