I have used Soviet RPN calculator at my school years. It was not compatible with TI or something Western, but as I know ideologically it was very close.
What also interest, in early 2000s, Russia made modern remake, with much improved performance and added digital i/o, and compatible with old programs (even emulated some old glitches), so it could really run tons of programs one could find on old books/magazines.
I could not recommend anybody to buy Russian calculators, just want to say, this is very significant niche (RPN), but hugely depend on compatibility (with old software and old books) and on nostalgia.
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