I should add that, if it's seriously off the face, as you say, that could be a deal breaker. I'd send it to a top gunsmith for his opinion and, depending on what he has to say, make the decision. Action hinge pins can be replaced and I did this recently for a Simson side by side. It's now tight-as. Also, I saw today a Holland and Holland side by side of around 1890 vintage that had the front hook packed, possibly by the factory as it looked like a very well done job. But it's not a job I'd ever trust to the local blacksmith who fixes the odd gun.

I saw one break-open gun sold well off the face that, once the auction buyer got an opinion on it afterwards, led to a lot of ill feeling and I think it was eventually returned. Drillings are very expensive in the US, so this gun could be a short cut to a bargain - or not. Do your homework first to avoid surprises.