1986 Seiko 7A28-7120 'Gen 1' MoD aircrew issue chronograph

The watch case is in superb, clean cosmetic condition with only minor marks and small knocks from use/storage. The case back is in very clean condition with some small marks. The dial and hands are in excellent condition. The crystal is a replacement. Please refer to the images to make your own judgement about the condition of the watch.

Mechanically the watch had a full stripdown, clean and service in January 2026, with full new gasket set including OEM crystal gasket. Images of the rebuild have been included in the listing.

The case parts were stripped including removal of the pushers, and ultrasonically cleaned. The pusher gaskets have been replaced, greased and the pushers refitted. The movement was fully stripped, mechanically and ultrasonically cleaned using waterless solutions and hot air dried. The movement was rebuilt and lubricated in accordance with the Seiko technical manual and a new 394 battery was fitted. The back gasket and crown gasket have also been replaced and greased.

The watch has been fully tested and is in full working order with all functions operating correctly including chronograph start, stop and reset, test function, lap timer and manual chronograph start position adjustment. 

The watch has been regulated on a quartztester machine and on the bench is running at +0.02 seconds per day, equivalent to +/- 0.6 seconds per month, well within the +/- 10 seconds per months specification. Note that accuracy in use may differ from this figure.

All round an excellent, fully sorted example, supplied on a new black/grey 'James Bond' NATO strap.

The watch is absolutely suitable for everyday use, but it is vintage watch so is not recommended for sports or use in extreme conditions. The watch has not been pressure tested so water resistance is not guaranteed. This watch is covered by our waterproof 6 month guarantee.

Issued: Yes

Issue details: UK, Royal Air Force, Royal Navy, Army aircrew issue

Date of manufacture: 1986

Rarity: 11307 issued altogether, 1475 during 1986

Movement: Seiko cal 7A28

Diameter: 37mm

Lug width: 20mm

Hacking: Yes

Other features: Chronograph centre sweep hand, 1/10 second counter and minute counter, lap timer and chronograph test function.

Case back: Screw down

Screwdown crown: No

Bracelet: NATO strap

• UK MoD aircrew issue quartz chronograph

• Not traded before on civilian market - you will be the first to wear it since MoD ownership

• Legendary 7A28 movement

• 1475 issued in 1986

• Recently full overhaul

• Superb condition

• Supplied on new NATO-type strap

• 6 months non-waterproof guarantee

You will find many examples of Seiko Gen 1s on offer, with a range of prices from cheaper than this one to more expensive, but very few of them have a recent photo-documented overhaul. 

While the 7A28 is a robust and reliable movement, it is also complicated, with 4 separate step motors to operate the different time-keeping and chronograph functions. Over time, dirt and moisture can get into the movement via perished/dry gaskets, and the lubricant begins to become dry and gummy. The cumulative affect is to cause friction in the mechanism which results in faults with the different chronograph functions. If left unresolved this will cause excessive wear in the movement and the problems will only become worse. Dirt also builds up inside the pushers, which then holds moisture which can get into the movement, and which can stop the pushers from correctly functioning - so the case and pushers also need to be stripped and cleaned for the watch to remain in good working order. Even if the watch is sold in good working order, with an unserviced watch it's just a question of time before it will need attention - and that could be expensive (a full service can be around £250).

If you buy a serviced Gen 1 you have piece of mind that the watch is not only in full working order but clean, lubricated, regulated for accuracy and good for many years to come