Atocha / Santa Margarita Shipwreck, Silver, Reale, 11g (+ paperwork)

Description

Atocha / Santa Margarita Shipwreck Silver Reale (and paperwork)
This coin was recently found in a large envelope (with the paperwork) in a box of papers, envelopes, and books that was purchased during a driving trip to Florida approximately 15 years ago.
None of the other books, letters, or papers in the box have anything even remotely to do with the Atocha, Mel Fisher, coins, treasure hunting, etc.
Here is the information that I have:
After reading the letters, newspaper clipping, etc, I did some online research and this appears to be a coin from the Atocha/Margarita shipwreck discovery by Mel Fisher. It says "Frag" on the Mint line, which seems to mean fragment. Also guessing, by its size (11 grams - 25mm x 38mm) I believe it is an 8 Reales coin fragment.
The paperwork consists of copies of:
-A Mel Fisher Treasure Sales Appraisal Certificate (see scan) with which I am unable to make any connection to the coin.
-A newspaper clipping (see scan) concerning Maggie Taylor's investment in the treasure hunting/salvage of the Aocha and Margarita.
-2 pages (see scan) of Marjorie Taylor's investment breakdown .
-3 letters (see scan) from Mel to Marjorie spanning 1971, concerning her investment and the progress on the hunt.
I can't find any connection to the actual coin with the paperwork, it just seems to be background about where the coin came from.
If anyone has any questions or more information to add please email.
Thanks.
On Sep-11-21 at 16:19:49 PDT, seller added the following information:
9/11: A couple things I would like to add after getting a few questions...
The slide-in description card is actually 2 cards but there is nothing on either side of the 2 cards.
The coin is a tiny bit concave on the x side.
I tried to add or replace photos for more clarity of some of the images, but I wasn't allowed to make any changes to the photos. So, if anyone is looking for a specific photo, message me and I can add a photo to my response.