I decided to put it here among watches, because it has in its construction fully functional watch module from Elektronika 51.
Here it is. One of the first Soviet pocket micro computers with matrix display and data bank function. It can be used as normal calculator with most useful functions, data bank for 100 phone numbers, schedule, notes.
Partially it is based on MK-85 pocket microcomputer, the first one Soviet microcomputer with BASIC. MK-85 looks like Casio FX700P, but inserts are different - nothing common at all.
Elektronika MK 87 was represented to delegates of XXVII Congress of the CPSU in 1986, but was produced a year later in 1987 in the 70th Anniversary of October revolution. So 87 means the year of production, like in MK 85.
MK 87 looks a bit common to Casio PF-3000, but also from the first glance. Insides are fully designed in the USSR. THere were produced approx 8000+ devices - the qty of delegates of Congress. It hadn't been in mass production. My sample was produced not earlier than in March 1987 (inscriprion on the watch module).
Data bank has 6! power cells inside. Four 357 cells for data bank, 371 for watch module and lithium 2016 for memory. Device still in the working condition, but it has a few bugs, also display dots has different contrast. It will be 30 years old soon :)
The proof of the pudding is in the eating...