From the eBay shots it appears to be a 28 with a 31 emblem. Be careful buying shells that need replating. If there is a lot of pitting it can get very expensive —I mean, like $1000 or more, at least in the Pacific NW. May be different where you are. I think the shape looks right.
If you don't plan to replate, though, the bids so far seem about right. I wouldn't go above $75.