This challenge coin measures 1 5/8 inches in diameter.
This coin is made for the "Slimy Pollywog" who earns the label of "Trusty Shellback" through Royal Order of King Neptune's Ancient Order of the Deep’s crossing the equator initiation .
Definition of Shellback from Wikipedia:
The ceremony of crossing the line is an initiation rite in the Royal Navy, U.S. Navy, and other navies which commemorates a sailor's first crossing of the equator. Originally the tradition was created as a test for seasoned sailors to ensure their new shipmates were capable of handling long rough times at sea. Sailors who have already crossed the equator are nicknamed (Trusty) Shellbacks, often referred to as Sons of Neptune; those who have not are nicknamed (Slimy) Pollywogs.
"King Neptune and his court" (usually including his first assistant Davy Jones and her Highness Amphitrite and often various dignitaries, who are all represented by the highest ranking seamen) officiate at the ceremony, during which the Pollywogs undergo a number of increasingly disgusting ordeals (wearing clothing inside out and backwards; crawling on hands and knees on nonskid-coated decks; being swatted; being locked in stocks and pillories and pelted with mushy fruit; crawling through chutes and large tubs of rotting garbage; kissing the Royal Baby's belly coated with axle grease, hair chopping, etc), largely for the entertainment of the shellbacks.