Had a brief nosey through Wikipedia. So, there were four known Spanish ships sunk near Panama 29th Nov - 3rd Dec 1681 via a storm. The coin appears to be a Spanish Real of the era which you've dated to 1679.
From a relatively brief poke around the internet, only the wreck of Nuestra Senora de Encarnacion has been found - in 2011. It left Spain in January 1681 so would've had the opportunity to collect a (relatively) new coin. So far as I can tell, the other three ships in the fleet that sunk are still lost to the depths or were wrecked so badly that nothing remains of the ship.
Assuming you've not had the coin longer than 2011, and the rest of the story you've been told (I.e. A shipwreck off Panama) is true, then I'd place the Encarnation as the most likely candidate. Other known Spanish ships known to have sunk around the time aren't in the right area - most are more central Caribbean or Florida.
Hope that was of some help, I'll include my starting point links for Wikipedia below.
LIST OF SHIPS: en.wikipedia.org/wiki/List_of_shipwrecks_in_the_17th_century
ARTICLE ON ENCARNACION + description of storm: en.wikipedia.org/wiki/Nuestra_Señora_de_Encarnación
Thanx for the research. Unfortunately, the coin was obtained 20+ years ago. The diver was an US Army soldier stationed in the Panama Canal. He dove on a wreck which he did not identify. He is now dead and I did not get the chance to ask him more questions. In fact, he did not really want to reveal where he dove--since, according to him--no one was supposed to be diving on this shipwreck.
Thus, is my problem of having a coin from an unidentified wreck near the Panama Canal. I have been told that knowing the wreck can increase the value of the coin. This is the only Piece of Eight I own.
I will follow your lead and see if anything else reveals itself.
No problem at all. If he suggested no-one was supposed to be diving on the wreck, that would imply that the shipwreck was known about. So, you'd be looking for a shipwreck in the area discovered before ~2000 if he'd had it ~20 years or so. The alternative would be if he had said he'd discovered it, but decided to keep quiet about the wreck for whatever such reason. I.e. He found it before it was officially discovered. In which case, the Encarnacion could still be a possibility.
In my, admittedly limited, knowledge - simply saying an item was discovered on a specific ship is rarely good enough. You need to be able to prove some level of provenance to see the value increase. That would be things like knowing that the ship's cargo was, for example, freshly minted silver & gold coinage. OR having some official certification - that could be issued by a salvage company or at a national level. E.g. “Company -x- certifies that this coin was found on wreck of -y- in -date-. We are authorised to retrieve & sell shipwreck items by the Government of Panama”.
And even then, if price only dramatically changes if the ship was involved in a “pivotal” moment in history. A coin which could be proven to have been on, let's say the Titanic, when it sank will have a value somewhat above the typical trading value of the coin. Everyone's heard of the Titanic, it was a major incident. You get collectors for coins, for Titanic memorabilia, and general maritime items. That competition increases the value.
I have a coin which, according to the accompanying certificate, was found on the wreck of Admiral Gardner. All the dates & history checks out, as does the company who did legitimately retrieve items from the wreck to sell. I paid the princely sum of £2 for it. Whilst I did get a bargain on it, even now they're readily available for ~£25
If the coin existed outside of the hoard found on the wreck, then without some sort of certificate, there's no proof yours came from a ship wreck. Perhaps the soldier bought it as a souvenir, or maybe he won it in a bet. Of course, the original source still could be a shipwreck, but it could also be just about anything else. If you're looking to sell it, you should really expect to get typical trading value. You can always include the story as an “alleged history”. But before you spend hours & hours researching & trying to prove history, it might be worth seeing if all that work does actually result in higher values from other coins from that wreck (or similar time periods).
