Nothing about the devices/detail looks anomalous at first glance... I sort of like the shape of the planchet. I don't like that in reviewing about 15 examples quickly, I don't see a match to that positioning of the lions/castles (but that's not exhaustive).
As Bob laid out, no chance of contemporary counterfeit... Not sea salvage... "Maybe" ground recovery from looking at the reverse? However, those bubbles look either fire-caused or casting-caused. Interesting study piece... it at least has a chance. In the interest of perhaps finding the easy solution, do we have any other info about the source from whence it came? Any other pieces it was keeping time with?
One aside - if genuine, with those surface issues, this should be more like a $400-500 piece. These are scarce, but not impossible.
PS - posting this in Mathieu's showing of his 1810 Santiago also. Search "Major Chilean Coin Collection Stolen on that other major forum...
"Santiago Chile authorities are investigating the theft of a major Chilean coin collection valued at hundreds of thousands of dollars.
"The collection included a complete 8 Reales series of Santiago which includes a Pillar dollar and a 8 Reales CIII type, in addition to all the dates for Charles IV and Ferdinand VII in all varieties, a series that includes 70 different pieces. Also taken were approximately 20 Chile Independent coins and several hundred colonial coins, republican, 200 pattern pieces and hundreds of error coins (approx 400). Coins from Peru, Mexico and Potsi, including a collection of approximately 300 silver cobs. Thousands of coins were taken in this offense."
Also contained in that post, this apparently is a link to a local article in Spanish:
http://www.emol.com/noticias/nacion...illones.html