Cóbh

The letter is usually explained by an Irish port that has since changed its name back.

Royal Navy decoys worked out of Queenstown in Cork Harbor during the First World War, and many were converted at the Haulbowline dockyard there, which is the standard explanation for the Q. No Admiralty statement confirms it, so the letter may have been nothing more than a file designation. Queenstown was renamed Cobh in 1920.