Introduced in 1946, the Calibre 476 came 20 years after John Harwood and Blancpain presented the first automatic wristwatch and 15 years after the Rolex "Perpetual" went into production. It was a bumper movement, not a 360º rotor as in today's watches, but it boasted a respectable 40 hour power reserve and was accurate enough to be certified a chronometer in later years. It ran at 18,000 vph.
Note that Cal. 476 is often stamped "12A", leading to confusion about the naming of this movement.