Atalla Box
Mohamed Atalla's early-1970s encryption box for bank PINs, widely regarded as the first hardware security module.
Mohamed M. Atalla, the same engineer who co-invented the MOSFET at Bell Labs, left the semiconductor business and founded Atalla Corporation in 1972. The problem he went after was cash machines: PINs were transmitted and stored in ways that staff and attackers could get at. The Atalla Box encrypted the PIN at the terminal and verified it inside a sealed unit at the bank, so it never existed in cleartext on the bank's computers.
The idea that keys live in a box that only performs operations and never hands them out is exactly what modern HSMs are built on. Tandem Computers bought the company in 1987, and the Atalla name carried on as a line of payment HSMs for decades afterwards.