This is a special shipwreck coin, that seemed to be doomed from the start. Spanish coins struck in the 1600s marked their date with the last two numbers. For example - “1653” would be shortened to “53”
But this piece is the first I’ve seen to contain 3 numbers for the date. And they picked a super convenient year to do so, 1666. Which is displayed at “666” on the coin. Fascinating.