The watches of the British Royal Navy have long been favorites with collectors, the most famous being the mythical “MilSub” Rolex Submariner issued to Her Majesty’s frogmen for decades. The characteristics that distinguish the MilSub from its civilian counterpart – sword hands and a fully marked bezel – weren’t of Rolex’s devising however. They were copied from Omega. While early 5512 and 5513 Submariners were favored by British quartermasters, in the mid-60s, the new Omega Seamaster 300 was considered a superior diving instrument and adopted for use by Royal Navy divers. These watches are distinguished by the required welded strap bars, military engravings on the caseback and a “circle T” on the dial, indicating the use of tritium for luminescence. Some later versions also feature an oversized triangle for the 12 o’clock dial marker, a feature that also made its way onto civvy versions. These military SM300s are rarer than Rolex MilSubs due to their having been issued for only a couple of years, yet don’t command nearly as high of prices, making them a great vintage buy.

The SM300 was only issued to Royal Navy divers for a few years before it was phased out in favor of the Rolex again, the latter of which was forced to copy the former’s hands and bezel for readability. Where the Rolex was superior was in water resistance and this was thanks to its bulletproof Twinlock screw-down crown. The crown was Omega’s Achilles heel. They had experimented with a pressure-sealing crown they called the “Naiad” (“water nymph” in Greek), which sealed tighter with increasing water pressure. What was a good idea in theory proved less reliable in the real world and the Naiad crown had a tendency to leak at shallower depths where pressure was less. Omega-restored versions usually had screw-down crowns installed.

The second generation SM300 lasted until 1970 when it was discontinued in favor of watches more keeping with the times – funky shapes, experimental bezels and abyssal depth ratings – the so-called “Big Blue” Seamaster chronograph, the legendary Ploprof and the angular SHOM, among others. The family resemblance to earlier Seamasters disappeared altogether, losing the classic lines of the CK2913 and 165.024. This divergence of design and explosion of reference numbers told the tale of a brand in trouble, as Omega fought to stay relevant in the dark days of the 1970s. I’d like to think that if Omega had kept producing the Seamaster 300 as it was in the 1960s, with incremental improvements, it would be as much of a popular, desired watch as its old rival, the Rolex Submariner.