The ceremony of CROSSING THE LINE  was created so seasoned sailors could test their new shipmates capability to handle long, rough times at sea.    It commemorates a sailor's first crossing of the equator.     Sailors who have already crossed the equator are called (Trusty) Shellbacks, often referred to as Sons of Neptune (Ed Cafferty's gold colored certificate).   Those who have not crossed the equator are called (Slimy) Pollywogs.

"King Neptune and his court" officiate at the ceremony, which includes his first assistant Davy Jones and her Highness Amphitrite and often various dignitaries who are all represented by the highest ranking seamen.    The Pollywogs undergo a number of increasingly disgusting ordeals, wearing clothing inside out and backwards; crawling on hands and knees on deck; being swatted with short lengths of fire hose; being locked in stocks and pelted with mushy fruit; crawling through chutes and large tubs of rotting garbage;  kissing the Royal Baby's belly which is coated with axle grease, getting their hair chopped off and such, largely for the entertainment of the Shellbacks.

Once the ceremony is complete, a Pollywog receives a certificate declaring his new status.     The Golden Shellback is one who has crossed the equator at the 180th meridian, the international date line.  Note Ed Cafferty's orange certificate stating he did this.
 

Information from various sources including Wikipedia  & JVH

#60

#61

#62

#63

#64

#65

65a
Walter Steward, Paris, AR; Leon Strang, Camden, NJ; Harry Lyles; Gumbais; Billy Chandler;
Leroy Johnson; Odell Mahan, AR; Nick Estrada, KC, MO; Tannehill; Dom Turso, NYC

#66

#67

#68