Manchester Baby Lost
The machine that ran the first stored program — 17 instructions on June 21, 1948, proving the Williams tube memory worked. Scrap within a year; a replica runs at the Museum of Science and Industry.
The Baby (SSEM) was built to test Williams's CRT memory — a tiny proof-of-concept with seven instructions. On June 21, 1948, Kilburn's 52-instruction program factored 2^18 — the first program ever run on a stored-program computer, anywhere.
It was cannibalized for the Manchester Mark 1 within the year; the replica at MOSI was built from photographs and memories. Kilburn later said the machine's significance was that it was 'small enough to be made to work.'