I remember. There was relative of MK-61, nearly fully compatible and in theory have extension port: https://en.wikipedia.org/wiki/Elektronika_MK-52 https://en.

I remember. There was relative of MK-61, nearly fully compatible and in theory have extension port: https://en.wikipedia.org/wiki/Elektronika_MK-52 https://en.wikipedia.org/wiki/Elektronika_MK-52 And sorry for Russian language link, for some reason I have not found English. https://ru.wikipedia.org/wiki/Электроника_МК-161 https://ru.wikipedia.org/wiki/Электроника_МК-161 https://web.archive.org/web/20140202161045/http://mk.semico.ru/dr_info21.htm https://web.archive.org/web/20140202161045/http://mk.semico....