The Standards Eastern Automatic Computer was built by the National Bureau of Standards in 1948. It started crunching numbers in 1950 and stayed in constant operation until... 1964! This early machine, festooned with vacuum tubes, lived well past the first transistorized computers. So what exactly is SEAC doing so far into the semiconductor future?
Selected Sources:
https://archive.org/details/circularofbureau551unse/page/n7/mode/2up - Circular 551
https://sci-hub.se/10.1109/85.238389 - EDVAC Draft Report
https://sci-hub.se/10.1145/1457720.1457763 - Imaging with SEAC