1971's Smallest Battery-Powered Calculator: Dictaphone 1680
Taking a look at the Sanyo ICC-82D, aka the Dictaphone 1680. The smallest portable electronic calculator with built-in display on the market in 1971! And one of the first hand-holdable battery powered calculators, period. It wasn't cheap either, costing 495 in '71 roughly 3500 with inflation!
Source: Lazy Game Reviews (2022-06-24)