Welcome to Treasure Net !!
IMO Potosi cob.
If assayer's initial is an "E" the 1952-1 678 Antonio de Ergueta . If initial is an "F" then dated 1697-1701 when Tomas Fernandez de Ocana was the assayer. Could be wrong, but that is my fist guess.
Don.....
XP Deus
Minelab Sovereign xs2a Pro
Minelab Sovereign GT
Minelab X-Terra 705
Minelab Explorer SE
Minelab e-trac
Tesoro compadre
Whites v3i
AT Pro
Teknetics Gamma 6000
Bounty Hunter Camo LS
Bounty Hunt
Superb find! I almost bought a house in Sag Harbor in the 90's but my job took me to the Philly area instead. Still kicking myself, seeing real estate prices the way they are there now. I always dreamed of detecting that area, even though I didn't start detecting until I moved away from the Island.
FYI, there are some sites I'm aware of very close by that I think may be very productive. Send me a private message and I'll clue you in!