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1951 IWC Mark XI for the Royal Air Force

36 mm
Very good

A Mark XI with a charming black tritium dial, a military stamped case, and the IWC 89 hand-wound movement.

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During World War II, IWC was one of twelve brands commissioned by the British Ministry of Defense to produce mil-spec watches meant to be worn by soldiers in the field. The MoD laid out a strict set of requirements these watches had to follow, including the usage of a black dial with Arabic numerals, luminous hands and indexes, a large crown, and a shock-resistant case. In addition, each watch was triple signed with the British military broad arrow on the dial, caseback, and inner case. IWC’s contribution to the “Dirty Dozen” was the Mark X, a beautiful time-only piece equipped with sword hands, small seconds, and the hand-wound caliber 83. 

The Mark X was decommissioned in 1948 and replaced by the Mark XI, which was brought up to the latest MoD spec and issued to pilots of the Royal Air Force. The new watch contained several upgrades to the dial and movement including the addition of the iconic triangle plot at 12 o’ clock, a paddle hour hand, central seconds, and the chronometer grade caliber 89—now protected by an anti-magnetic soft iron shield. Each Mark XI was subjected to a 44-day testing period at the Royal Greenwich Observatory before being distributed to RAF pilots, who relied on these instruments to accurately time their missions and resist magnetic fields within the cockpit.

Due to the rigors of their usage, Mark XIs were routinely sent in for regulation and parts replacement to ensure they maintained the standards set forth by the MoD. By the mid 1960s, most of these watches had their original radium dials replaced with newer tritium versions marked with a circled “T”. The Mark XI remained in service until the early 1980s where it was phased out and ultimately unreplaced by the MoD. Yet the DNA of this iconic piece has lived on in subsequent offerings from IWC, and there is perhaps no watch that has influenced the brand’s modern design and ethos more than this one.





Mark XI for the Royal Air Force





Case Number:


Case Material:

Stainless steel


36 mm

Lug Width:

18 mm


11.5 mm


46.5 mm










IWC 89


Gray NATO textile strap

Max Wrist Size:

Hand model has a wrist size of 6.2 in


UNWORN: Case is pristine with no signs of use. Original stickers may still be present. Dial, hands, and lume have no imperfections and may show natural, even aging.

MINT: Case has only a few superficial hairlines. Lugs are thick, full, and sharp with superb finishing. Dial, hands, and lume may have micro imperfections visible only with a loupe.

EXCELLENT: Case has very light scratches or nicks. Lugs are thick, full, and well-defined. Dial and hands may have imperfections visible upon close inspection. Lume is fully intact and may show slight discoloration.

VERY GOOD: Case may have a few moderate scratches or nicks. Lugs are thick and full but may have softened edges. Dial and hands may have light stains or marks. Lume may have cracks or discoloration.

GOOD: Case has many scratches and nicks. Lugs may show signs of moderate polishing with worn edges. Dial and hands may have noticeable stains or marks. Lume may be damaged or show significant discoloration.

Case: The stainless steel case has seen a lifetime of wear, yet remains in remarkable condition with strong lines and crisp edges. There are numerous hairlines, nicks, and small scratches, but none so great that they detract from the overall wearing experience. The lugs are nice and strong with excellent definition. The polished top of the bezel remains crisp at the edges, a good indicator that this watch has not been victim to the polishing wheel. The caseback condition is consistent with the rest of the watch, showing moderate, but not aggressive, wear. The model and serial number engravings remain sharp and deep.

Dial, Hands, & Crystal: The matte black dial and steel hands have been wonderfully preserved with light signs of aging and oxidation, but no major imperfections. The tritium across both is a nice shade of yellow. The hands have aged to be slightly darker than the hour markers. The acrylic crystal shows some hairlines and faint scratching, but still has plenty of life left to give.

Bracelet/Strap: The gray NATO strap is in fantastic condition with only light signs of wear. It has broken in just enough to become soft and pliable. There is no staining or major fraying present.


Timing: The watch has been measured with a timegrapher at six different positions. The rate, amplitude, and beat error are within acceptable ranges. While resting face up, the rate is +4s/d.

Functions: All functions including the crown winding and time setting are working as expected.

Service History: The watch recently underwent a full service by True Patina that was completed on 05/18/2023.

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What's Included

What's Included



IWC Mark XI for the Royal Air Force on a gray NATO textile strap.





Service record from True Patina dated May 2023.