8 reales coin certified w/ certificate from Treasure Salvors Inc. (Mel Fisher)

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What would be the worth of a silver 8 reals coin certified with a certificate from Mel Fishers company on the open market today? I am considering buying one from a friend who knew the Fishers. The coin is from the 1715 Fleet and they have none left.
It was found on site designated C1329 in the State of Florida archaeological file. PLEASE, help me with an actual market value.

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The Fisher site had no info on the coin that I have. Mels Daughter is currently working the site again. They have no more of these coins in stock, therefore they can't give me any info. Thanks for the reply. HH
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[cedarratt]

my dad got a silver reall in trade that was supposed to be from the atocha. But the guy who had had lost the paper work. My dad has known him for a long time so it is probably legit. I had heard that for a fee they would re certify a coin assuming it was one from the wreck, since they had photographed everything before they sold it or so I heard.

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Yes I do have photos on the original bill of authenticity from the Fishers. Atocha artifacts are much more valuable, according to the treasure salvors aka Fisher web site, they may be as much as twice the value. The one I have is whole (27grams). I was just wondering what the value to a collector is. Although I have no intention of selling it, my curiosity has gotten the best of me. Thanks for the response cedarratt and HH.
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