Check out this bad boy I just laid my hands on: a top-notch Friden 130 "desktop" calculator made in 1964. Absolutely massive, over 40 lbs and originally costing as much as a car. CRT vector-drawn digits - no small feat in the days before complex integrated circuits. All four basic arithmetic operations implemented solely with discrete transistors. The device uses an acoustic (magnetostrictive) delay line memory for storage, because transistor flip-flops were expensive to construct.
The calculator uses reverse Polish notation (long before HP) and displays all four stack registers at once (with no zero blanking).