The value of an artifact is directly related to the amount of accurate data available about the item. Sometimes called, provenience, other times called pedigree.
Without the paperwork a dog is just a mutt. With the papers the dog has lineage and pedigree and is worth a lot more.
The more you can document.... the more paper you can produce from experts,( not just your opinions.) in the field of colonial anchors in the new world, the more bucks you can command. Location data is great but assumption, as to origin, is just speculation and has little value.
All the authentic 17th. century Spanish colonial anchors that I have seen all had sharp pointed flukes.( about thirty anchors.) The anchors from other, non Spanish sites ( about sixty.) had palm shaped flukes like yours.
That is, until you get to the mid to late 18th. century, then the Spanish seemed to adopt the palm shaped flukes. Some of those anchors were possibly purchases, swaps, or salvaged.
I think you need to do more research on the origin of your anchor, in order to get that price up there where it is worthwhile to recover, preserve and properly document this artifact, then sell it to someone who can appreciate it's unique history and pedigree.
Best of luck.
Splash,
Donovan