If you check the right grip panel's backside, you may find the serial number there in pencil; it could be really faded, sometimes a high-power flashlight held at various angles reveals it, which would confirm that the stocks are original to the gun. However, absence of the pencil number doesn't mean they're not.

If you do get it, I think based on the second photo (unless it is a weird effect of the lighting), the chambers can use a good cleaning .

If it were just on sale somewhere, I wouldn't pay more than 350 to 400 either, but I would pay 500 to keep an heirloom in the family.