I'm considering buying a Marlin 336, 1978 vintage with walnut stock. It is in very good condition (95% maybe) but it has a hairline crack in the stock that runs forward from the butt plate about one inch. It is in the middle of of the butt, and not near the butt plate screws, and only visible on one side. It has not opened up at all and is barely noticeable. Does this devalue the gun much and is there any chance of it opening more at this age?