That is a very cool find. I would recommend electrolysis to try and remove some of the corrosion. But of course, the best thing to do would be to take it to a museum and ask their advice on what it is, and how best to preserve it.
The original post included the size: Found this 1/4 mile south of Jupiter Inlet. On the beach, at a depth of 3" and measures 14" long x 7" wide. Can anyone identify this?
Too small to be an anchor or even a grappnel hook IMHO.