U.S. MERCHANT MARINE ENGINE OFFICER COLLAR DEVICE

A propeller with two blades facing down was used in the United States Maritime Service as both a Warrant Officer specialty mark for Machinists and a branch of service insignia for Officers in Engineering. In today’s Merchant Marine, it is a departmental insignia for Marines serving in the Engine department who have qualified for at least Third Assistant Engineer, Steam and Motor Vessels of any Horsepower by passing the United States Coast Guard examination.
 
The Engine Department device is worn in tandem with a pin-on metal rank device, with the propeller placed on the wearer’s left collar and a rank insignia worn on the right collar. Both devices are centered on an imaginary line that equilaterally bisects the collar point; the propeller device is oriented so that a single blade is pointing toward the neck and the imaginary line also bisects the two bottom blades.