The Omega Speedmaster Professional ref. 105.012-66 is one of the most iconic and collectible vintage Speedmasters, produced in 1966 and powered by the legendary Omega Calibre 321, a hand-wound, column-wheel chronograph movement also used in the Speedmasters worn by NASA astronauts during the Apollo missions. One of its most desirable features is the original “Dot Over 90” (DON) tachymeter bezel, where the dot is positioned above the number 90—a highly sought-after detail that significantly enhances the watch’s originality, authenticity, and collector value.