It's upside down, and I think it is too far gone to be read, except for the second-to-the last kanji which is 宗 (sō or mune).
If my guess is right, the lacquered mei is trying to be 囗囗正宗作 (something Masamune-saku). In other words, "by Masamune", in which case the writing is 99.99% certain to be a forgery.