Type

Used RPN scientific calculators

Scientific HPs in portrait bodies, from the 1976 HP-27, a red-LED Woodstock that put science and finance on one keyboard, to the Pioneer models of the late 80s and 90s. The HP-42S of 1988 runs HP-41 programs on a two-line display, with matrices, complex numbers and a solver, and the 32SII of 1991 is a smaller programmable with an equation solver and integration. The Pioneers run on button cells and rarely fail, though dust can get trapped behind the display. The 42S has a modern clone, the SwissMicros DM42, built around the Free42 rewrite of its software, so check for HP branding.

3 calculators we cover.