Here's a bullion on black Colonel's slip on from the old work dress uniform of the Canadian Air Force, Army and the Navy.  A sailor who wore this was a full naval Captain, often a ship Captain.  It was worn on the jacket epaulettes as well as the collared shirt worn below.

It's 3 3/4" tall and in unused condition.

Good luck bidding and thanks for looking at another auction from The Mighty Atom.