Model: 7 (YU 101 - ю 101)
Cell type: Selenium
Measure type: reflecting/averaging; 2D incident with attachment
This the first update of the ubiquitous Leningrad 6. I wouldn't call it rare, but it seems to be less available than the Leningrad 8, and both are dwarved by the Leningrad 6. Frankly I can see why; it seems like a big step backwards. The Leningrads 1, 2 and 4 all had the diffuser bar as a separate accessory which was kept in the leather case. The Leningrad 6 went with a built-in diffuser; now on this 7 we're back to having it as a separate accessory in the case.
We've also dropped back to the spring-loaded slide button and selenium cell.
Worse—all of the previous Leningrads had cases which were fitted so that the meter almost never need be taken out of the case, which offers great protection. Not this one: now the case is a pouch and you must pull it out in order to use it.
Honestly, if it weren't marked differently, I would thought this a Leningrad 5, as it seems to have a great deal in common with the Leningrad 4 and very little with the 6.
That's Russian technology for you.
Here is a cross-reference chart for film speeds (ASA / ISO / DIN / GOST / others) .
Alfred's Camera Page has a nice write-up on this meter.