The BM-51-2 stereo microscope appears in LOMO sales catalogs, even though it was manufactured at the KOMZ factory - Kazan Optical-Mechanical Plant - No. 237, Kazan.
Although this model looks like a product from the 1950s, it was produced at least until 1996 - concurrently with the MBC-10 model (sic!).
Magnification: 8.75x
Eyepieces: Interchangeable, with a mounting diameter of 30 mm
Working distance: 150 mm
Weight: Less than 1 kg including the stand (very lightweight)