Heavy old forged iron hook or hand gaff. This is an unusually heavy duty hook with a sturdy forged hook. Much better than the hooks made from round iron rod just bent into shape.
I really like the non-round handle on this hook. With that you can really get a good grip that won't turn in your hand.
This has worn old red paint and is stamped "DLI" (I think? - probably an owner's initials). It's about 11" long and 4 1/4" across the grip.