The seller doesn't think it's a proof, but I can't remember seeing such square rims on a business strike--what do you think?
I think I agree with you. The strike is so hammered and the surfaces so clean, that, on top of the square-looking rims, I think it is a proof.
I suspect this is an impaired proof. The raised area on the neck is probably dirt--I don't see a match to any known variety.