I looked over a Grove 10 ga hammer gun in Alabama a few years back...looked pretty well made. Sadly it had sewer pipes for barrels (severly pitted).
I could've got it for $400 but passed because of the nasty bores.

Could you show a picture of the inside of the locks ?

I'd say the crack could be fixed by the right guy....if it had good bores and the price was right I'd go for it.