CASIO fx-4000P scientific calculator from 1986

[gning]

I did once own an HP with RPN, but only the 21, which had no programmability, and which used crappy NiCd batteries that essentially nullified the permanence and durability of all the other parts. I think I went through three packs before giving up.

The Casio was a big improvement despite its mushy buttons and low-contrast display. I still have the vinyl case, cheat card, and manual.

And hey, I found one of my old fx-4000P programs in a notebook.