Welcome to the forum, and congratulations on picking up a Mark 11 — it is a wonderful reference, but also one of the most faked and "married" military watches out there, so caution is wise.
A few things worth checking while you wait for the expert verdict:
1. The movement serial — an Extract from the Archives from IWC will confirm the delivery date and destination. Mark 11s went to the RAF, RAAF, RNZAF and others, and the records usually match.
2. Military markings — the broad arrow and service markings on the case back should be crisply engraved, not laser-etched or soft. Many fakes get the depth and font of these wrong.
3. Dial and hands — original Mark 11 dials have very specific printing, and the hands should be the correct sword style with aged lume that matches the dial plots. Mismatched lume colour between hands and dial is a red flag.
4. The crown — original crowns are unsigned and of a particular profile; replaced crowns are extremely common.
Thomas Koenig is indeed the right person to ask — his knowledge of the Mark 11 production is unmatched. Good luck, and do share what you learn!