Salvaged by Art McKee, Jr. from the Capitana wreck sunk in the hurricane of 1733.
21 galleons sank off the Florida Keys in route to Spain when hurled into the Florida coast. Lost until discovered in the 19th century by Art McKee & other first tier salvagers like Martin Meylach.
Original certificate hand signed by Janet McKee, wife of Art McKee in 1980, 3 months before he passed away. 
This coin was probably discovered in the mid 1900’s I speculate. 
One fascinating aspect of the certificate besides being colorful is the seal with a imprinted silhouette of the gold coin. It appears to have been pressed & reverse burnished to leave a reverse print inside the McKee’s Sunken Treasure Museum corporate seal dated 1949.
The coin is 20mm wide & 6.6grams,  hand struck. Appears to be Philip III, Assayer B, 1598-1621 with S over the B. The Capitana wrecked during Philip V. Still researching this data.