Crossed Anchors on the webbing between the thumb and index fingers marked a bos’n’s (or boatswain’s) mate.
A Harpoon marked a member of the fishing fleet.
Hold written on one set of knuckles and Fast written on the other was meant to give a sailor good grip in the rigging.
A Shellback Turtle or King Neptune was earned when a sailor made it across the Equator.
A Sparrow or a Swallow tattoo would go to a sailor for every 5,000 nautical miles they traveled–a swallow because it can always find its way home.