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IWC Mk.XI c.1957 RAF Pilot's Air Chronometer Watch - Mark 11 - International Watch Co.


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A rare and desirable Military Issue International Watch Company Mark 11 (Mk. XI) Post-WWII Air Chronometer Pilot's watch c.1957

A revolutionary piece of kit for the British Royal Air Force, the Mk. 11 allowed for a wholly different class of navigation as the aerial conflict intensified during the Second World War. This was to prove essential for coordinated bombing runs, and was built with the aid of military pilots from the Second World War. This watch was used by the navigator in an RAF plane in conjunction with a bubble-sextant to calculate the exact latitude and longitude of the aircraft. This method was in principle the same as that used by sailors to calculate their position ever since the development of the marine chronometer by John Harrison in the mid-eighteenth century. 

Though they weren't produced in large numbers, and many saw decommission from military service later in their lives, a few live on with a firm reputation behind them. Many forum browsers and watch collectors consider these pieces to be the most desirable and esteemed British military watch out there. Though the Dirty Dozens may be harder to find due to there being 12 of them to complete a set, the IWC Mk.XI is clearly a cut above most military watches by design. It does have a twin; the Jaeger LeCoultre Mk.XI, both of which are prized possessions and only slightly different. Both of these watches had varying dial specifications, with this one being a later and more legible dial having been produced in around 1957. 

It featured a soft iron core so as to fully encase the watch in an anti-magnetic housing, the dial also being made of iron so as to holistically encase the watch for accuracy's sake. The movement is extremely accurate, using a hacking complication to allow for the seconds hands to be precisely synchronized, and is chronometer-certified. The Mk.XI is the pinnacle of British military watchmaking: a carefully specified, refined design with supreme accuracy and solid craftsmanship. The case back is engraved '6B/346', the Ministry of Defence issue codes for the Mark 11 air chronometers. 

What's on offer

The watch does show minor signs of wear to the case, as one would expect from a watch from 1957, however, we hope you'll agree that these are remarkably insignificant for an old watch that may have seen active military service. It is, after all, a piece of history to be worn on the wrist, and the signs of wear are a part of this history. It comes with a 12-month warranty from VWS and is supplied in a leather presentation pouch. In March 2019 it was fully inspected and serviced by renowned military watchmaker John Senior so that I could occasionally wear it! I have loved having the watch and have taken good care of it, but it's time for it to meet its next owner. We purchased the watch from the original owner who bought this particular watch at a military surplus auction in New Zealand back in the 1970s and it was his daily wearer for a number of years after purchase and then sat in a draw for many years until we purchased it!

Additional information:

Made from

Case: Solid 36mm stainless steel, stepped bezel

Dial: Black, tritium inserts

Crystal: Plexiglas.

Bracelet: Sold with a Swedish deer leather strap, a ladder Bonklip-style military bracelet can alternatively be supplied (this is what the watch will have been first issued on).

Technical specifications

Movement Type: Manual winding.

Caliber: 89 Air Chronometer

Jewels: 17.

Purchase details

Condition: Very good, light signs of wear

Model reference number: Mk. XI IWC

Date / Year of issue: c.1957


Sold with 12-month guarantee.


Width (without crown) 36mm

Wrist size: Adjustable.