The Mk 11 wristwatch issued to the British Royal Air Force (RAF) was aviation’s equivalent to the marine chronometer- aptly nicknamed the air chronometer. Considered by many to be the original Pilot’s watch, it was made to the incredibly strict 6B/346 specifications and was one of the costliest commissions for a wristwatch by a military.

Some of the 6B/346 specs included the need to be regulated or adjusted to a chronometer level, the need for a hacking function, for it to be waterproof and to be anti-magnetic. These all stemmed from real needs from pilot’s in the RAF who relied on these watches both for navigation and timing purposes.

The Mk 11 watches can lay claim to be the first watch that was built from the ground up to be antimagnetic. With a thick iron dial and a soft iron dust cap, this created a Faraday cage, protecting the movement from any interference from the other equipment on the plane. It was, without doubt the most advanced watch issued to the military at the time.

This example features a ’T’ stamped dial, indicating that at some point, the luminous material was changed by the Ministry of Defence (MoD) from the harmful radium to tritium.

Often misnamed as a Mark 11 or Mark XI, the correct spelling according to the MoD is actually Mk 11. A perennial favourite amongst collectors partly due to its utilitarian no-nonsense layout and incredible quality, the Mk 11 is a great casual watch to wear as a daily beater. With only roughly 8000 pieces produced, this is considered a rare timepiece rich in historical provenance.