Nixie Tubes were state of the art in electronic numeric displays in early digital voltmeters, multimeters, frequency counters and many other types of technical equipment. They also appeared in costly digital time displays used in research and military establishments, and in many early electronic desktop calculators, including the first: the vacuum tube-based Sumlock-Comptometer Anita Mk VII of 1961. Later alphanumeric versions in fourteen segment display format found use in airport arrival/departure signs and stock ticker displays. Some elevators and pinball machines also used nixies for displays.
By the 1970’s they were almost completely supplanted by the cheap, long lived, low power-consuming seven segment LED’s. The nixie is a neon tube, typically with 10 stacked cathodes, one for each arabic digit.
Many folks are building their own clocks and wristwatches with vintage old stock tubes (watch examples #1, #2, #3), mostly uninspired designs but a few select people are creating interesting one-offs (Finkbuilt) and limited edition do-it-yourself kits (Klok).
Clock above was built by Longines, another amazing find Pieter Doensen showed me and wouldn't sell...