Seiko has produced quite a few watches for militaries throughout the world over the years, such as the 7A28-7120 and 7T27-7A20 chronographs.  The 7A28 and its successor, the 7T27, were known as the British Royal Air Force Gen 1 and RAF Gen 2, respectively, because as you may have guessed, both were well-known RAF-issued watches - like the 7A28 example here, with full military markings on the caseback indicating it was issued to the RAF. 
 
Seiko provided the 7A28s to RAF from late 1984 through late 1990, for a total of 11,307 examples.  7A28s came in two variants: one with Promethium-147 lume (signified by an encircled “P” on the dial; Promethium being a mildly radioactive emitter), issued to the RAF, and another version without luminous markings, which was issued to the British Royal Navy, primarily for crew on HM nuclear submarines.  Presumably, the lack of luminescent meant it could also be used in any environment where luminous material might interfere with sensitive military equipment.
 
By 1990, Seiko ended both the 7A28 and 7T27 (the earlier luminescent version) calibers in favor of the 7T32 alarm chronograph – Seiko went on to produce military-looking 7T32s subsequent, but none were military-issued timepieces.   However, in 1993, Seiko did supply the Royal Navy for sub crews from 1993 through 2000, in quite small numbers.
 
This Seiko 7A28 quartz watch comes with two nylon straps (like on many military-issue watches, springbars are afixed and non-removable), springbar tool, and hard plastic travel case.