Launch year
HP's dot-matrix years. The HP-28S and HP-42S launched in 1988, the 17BII business calculator in 1990, the 32SII in 1991 and the HP 48G and 48GX in 1993, all with alphanumeric LCDs that show menus and words. TI's solar TI-30 SLR+ dates from 1987. Most run on button cells or AAAs and keep their memory well, and the 48s and 42S have built-in self-tests that make checking one easy.
7 calculators we cover.
HP
Financial$25–$35 typical ask
45 on eBay
HP
RPN scientific$100–$170 typical ask
28 on eBay
HP
RPN scientific$190–$260 typical ask
19 on eBay
HP
Graphing$80–$140 typical ask
31 on eBay
HP
Graphing$100–$140 typical ask
28 on eBay
HP
Graphing$230–$340 typical ask
45 on eBay
Texas Instruments
Algebraic scientific$10–$25 typical ask
31 on eBay