The "Claddagh" is an Irish Symbol, that represents Love, Loyalty, and Friendship. (the hands represent friendship, the heart represents love, and the crown represents loyalty).
It's origins are from the Claddagh, Galway, Ireland. It was originally worn as a ring, where traditionally, if the owner of the ring wears it with the crown closest the finger tip, he or she is not available for courtship (is married/unavailable). To wear the ring with the heart closest to the finger tip, he or she is said to be unattached/single and available.
And a tip o' the hat to Alana for the detailed description. ;-)
24mm x 20mm By the each.