The Merchant Marine Meritourious Service Medal (MMMSM) was instituted by Presidential Decree of August 29th, 1944. Anyone serving aboard an American or foreign Merchant Vessel sailng under orders of the United States Maritime Commission or the War Shipping Administration was eligible for the medal. The medal could be awarded for merit or meritorious conduct as from September 1939 and after recommendation by the Administrator of the War Shipping Commission.
The action should have been insuffcent to merit an award of the Merchant Marine Distinguished Service Medal.
Multiple awards were marked with a suitable clasp, to be worn on the ribbon of the first award. The MMMSM could also be awarded posthumously.