In 1957 Omega introduced three professional watches at once, one for racing, one for engineers, one for the water, and the diver of the trilogy was the CK2913. It set the Seamaster's design language on day one: black rotating bezel, luminous broad arrow hands, high-contrast dial, and the Naiad crown, which sealed by pressure rather than screwing down. Eight sub-variants ran from the 2913-1 of 1957 to the 2913-8 of 1961, with hand styles and bezel details separating them, and US-delivered examples carrying the caliber 500 in place of the 501. The dial says Seamaster 300; the guarantee said 200 metres, which Omega attributed to the limits of its testing equipment rather than the watch. The file quotes both numbers because both are the record.
The reference's fortunes ride on one fragile part. The original bezel insert was bakelite, it cracks, and most survivors wear later service inserts, which is why an original-bezel 2913 trades in a different market from the same watch without one. That economics, a single brittle component carrying a large share of the value, is the same story the 6542's bakelite bezel tells over in the Rolex file, from the same years, for the same reason.
A trilogy founding document with a parts-driven market: the bezel, the hands, and the crown decide the money. Broad arrows invite swaps from lesser Seamasters, so the combination has to check out against the serial era, and the bezel's originality claim deserves the burden of proof.
Production windows and specifications compiled from documented collector references and period catalogs, cross-checked across independent sources; manufacturer records for this era are approximate by Seiko's own account.