You can use the WWII sticker.
{{World War II |branch= United States Merchant Marine |startdate= as dd mmm yyyy if you know it |units= if you know them |enddate=Service end date as dd mmm yyyy |rank=Enter the rank (Ex. Sergeant) here. Please do not use abbreviations like Sgt. |unit=if you know it |image=Wikimedia_Commons_photos-23.png }}