Although Merchant Navy officers wore the uniform of the merchant line they worked for, most merchant seamen wore civilian clothing. This created problems in the Second World War as they could be accosted by over zealous civilians who thought they were shirking the armed forces, or by dockside police who would question why they were hanging around a restricted area.
The Board of Trade therefore introduced a small metal lapel badge in 1939, with 734,000 being produced by the Royal Mint in that year. The badge consisted of the letters MN in a rope circle, knotted at the bottom and topped by a naval crown:
The badge, produced in sterling silver, was approved by the King and issued to men and officers of the Merchant Navy from the 1st January 1940 onwards. To allow it to be worn on the jackets commonly worn by civilians at the time, a half moon lapel fastener is attached to the back:
The badge was not just worn by British sailors, it was also issued to the crews of allied merchantmen and foreign nationals serving on British registered ships. Issue of the badge was ended on 31st December 1946, although there was no prohibition on men wearing it after that date.