The Aircraft Owners and Pilots association (AOPA) originally commissioned these pieces from Breitling in 1952 exclusively for pilots, and usually only for AOPA members. They provided an excellent and straightforward navigational tool for pilots, as the sliding rule could be used to calculate fuel consumption, the duration of flights and distances covered. The catchy name, 'Navitimer’, a simple combination of Navigation & Timer, soon became the official watch of the AOPA and the 'winged' logo of the AOPA replaced the Breitling 'B' on the dial. The earliest models did not tend to have a reference number, but were distinguishable by the engraved 'Breitling' and "B" logo engraved on reverse. Few stylistic or modification changes were made to this classic, except that between 1954-1955, the reference number 806 was assigned to the watch and the Valjoux calibre 72 replaced the original Venus 178 movement, seen here in this example. For obvious reasons, the majority of the Navitimers were cased in stainless steel. A very small quantity, starting in the 1960s, was made in 18k yellow gold. Such examples, especially when preserved in such wonderful original condition, are very rare collectors' watches.