Lenses engraved "8 1/2 x 6 1/2" will cover that format, which is larger than 5x7.
Are you a dolt? You might be, in which case welcome to the club. But be passing on what might have been a good buy is not particularly doltish behavior. If you know your Uncle Remus, remember the tarbaby.
Are you a dolt? You might not be, you could be averse to risk or, like me, completely unaware of such lenses' market value. I second Ralph's comment.