Terminated: unknown
It looks like a copy of the Rockwell 61R from 1974. Its keys have exactly the same shape, and all the keys are in the same positions. According to the elektronika.su (link validated 2026-01-26) website which talks about this calculator’s predecessor the БЗ-18M, this calculator was developed with three custom chips in the Sovjet Union. Its unclear if the chips of the Rockwell 61R were reverse engineered to produce this calculator. Forensic evidence seems to point in that direction. The rskey.org website has a page where specific calculation results of different calculators are listed and the results of the ELEKTRONIKA MK 18M and the Rockwell 61R for that specific test are identical. So please refer to that calculator’s page for specific operation details.
Some helpful translations:
- The Cyrillic symbol П is short for Память which translates to "Memory". Now the function of П+, П−, x↔П and П+x2 should be obvious.
- The Cyrillic symbol И in ИП is short for Индикация which translates to "Indication". Combined with Память this means that the ИП key shows the current value in memory.
- Use ЗАП to store a value in memory. It is short for ЗАПомнить which means "To memorize".
- The ДВ function undoes the last number entered. The Rockwell 61R’s manual calls this key the Data Recovery key, so ДВ might stand for Данных Восстановление.
- The ГРАД РАД slider is to switch between degrees (ГРАД; GRAD) and radians (РАД; RAD).