Between 1967 and 1971 the British military bought the 165.024 and modified it to specification: fixed strap bars instead of spring bars, a tritium dial marked with the circled T, sword hands, a fully luminous bezel triangle, and caseback engravings that identify the issuing service, 0552 for the Royal Navy, W10 for the Army. These are the most valuable Seamasters of the vintage era, trading at large premiums over civilian examples, which makes them, predictably, the most faked.
The forgery pressure runs in a specific direction: civilian 165.024s upgraded with military parts and fresh engravings. That is why the military file's examination order matters, engravings last, not first, because engravings are the easiest part to add and the provenance chain, issue records, family history, prior sales, is the hardest thing to counterfeit.
An issued military diver is a provenance purchase. The parts can all be sourced; the paper trail cannot. Buy the history, verify the engravings against known formats, and treat a bargain military Seamaster as exactly as plausible as a bargain MilSub, which is to say not.
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.