A few old-ish calculators I've accumulated.
Japanese made for German Olympia company. Based on Texas TMS0122 (1972) ,
with a ton of transistors to drive the display, which consists of a seperate vacuum
flourescent (VF) display tube per digit. Impressive modular construction, the back coming
off with a single coin-screw, and the boards unplugging. The keyboard uses reed switches,
with a magnet on each key. This is my favourite due to the wonderfully 70's space-age
Sperry-Remington Model 661D
A Japanese made 6-digit model using seperate VF display tubes. Decimals are limited to two or no places. Based on Hitachi HD32154P chip, with an NEC display driver. An unusual quirk of this unit is that it displays zeros using only the bottom half of the seven segment layout.
A.P.F Electronics Mark VII
Texas Instruments TMS0132 based, using a single 8 digit VF display tube. Interesting on-off switch - slide the button and the display cover pops up to reveal the display and turn it on! Nice 70's chrome styling!