Just looks like bad paint to me... What frameset is it? If it's mega cheap I'd take a gamble and if it's steel it could be an easy repair even if it is damaged.
It's mega, mega cheap for what it is. Sharing it because it's too big for me. If it was a 56 I'd be taking the risk. Seller has added a better photo (number 12) which shows it a bit better, but I think it's just unfortunate oxidation which looks worse than it is.
Just looks like bad paint to me... What frameset is it? If it's mega cheap I'd take a gamble and if it's steel it could be an easy repair even if it is damaged.