The Omega Speedmaster reference CK2915 was launched in 1957 as part of the brand’s trilogy of professional watches, alongside the Seamaster 300 and the Railmaster. It has a stainless steel case of 38.5 mm according to Phillips, a domed Plexiglas crystal, a dial with simple high-contrast index markers and the oval “O” in the signature, and the oversized arrow-shaped hour hand that gave it the nickname “Broad Arrow”. It is powered by the hand-wound calibre 321, a 17-jewel column-wheel chronograph, and its steel bezel carries a tachymeter scale. Phillips notes that it was the first chronograph to place the tachymeter on the bezel rather than on the dial, a layout that most sports chronographs later adopted. The case back is engraved “Speedmaster” around its edge. Production ran only from 1957 to 1959 in three series, CK2915-1, -2 and -3, with the -1 regarded as the first and most collectable.

The CK2915 was conceived as a sports and racing chronograph rather than a space watch, and its brushed steel bezel and broad arrow hands are early features that Omega later abandoned. The hippocampus engraving on the case back was added in later versions. In 1959 the CK2998 introduced a black aluminium bezel, and the 105.003 was the watch Ed White wore on the Gemini 4 spacewalk. After NASA tests in 1965 the Speedmaster was qualified for spaceflight, and the 105.012 and 145.012 are the two references known to have been worn on the Moon. The calibre 321, developed in 1946 by Albert Piguet of Lemania, powered all early Speedmasters until the calibre 861 replaced it in 1968 and 1969, and was reissued in 2019.

For Speedmaster collectors the CK2915 is the ultimate grail, and complete, original examples are scarce. Phillips sold a 1958 CK2915-1 in Hong Kong for HK$2,394,000, far above its estimate of HK$550,000 to 940,000. In 2021 a CK2915-1 dated 1957 sold at Phillips Geneva for CHF 3,115,500 against an estimate of CHF 80,000 to 120,000, a record for the model. The result later turned into a scandal: according to WatchPro, Omega, which had bought the watch for its own museum, described it as a “Frankenstein” assembled from mostly authentic parts of other vintage watches and alleged that former employees were involved. The episode remains a warning about originality in the vintage market. The CK2915 is no longer produced; the Speedmaster line continues in the current collection, led by the Speedmaster Professional, now fitted with the co-axial Master Chronometer calibre 3861.