First Tudor with a manufacture movement. Caliber MT5621. To commemorate this milestone the North Flag is fitted with a sapphire crystal display case back. Something Rolex/Tudor does extremely rare with serial production watches. The short-lived modern Rolex Prince models are the only others I can recall.
The long hour hand is reminiscent of the long neck “Mercedes” hour hands found on the very first Rolex sports watches from 1953-54.