So we dug this up at the old farm field today. It is 7 inches long about 56-58 mm across and is hollow up to about 3-4 inches in the bottom. It weighs 5 lbs. 13.3 oz. with whatever is in it (probably dirt but I'm not comfortable poking around in it). Is this a shell? If not, any ideas? Is it safe if hollowish? I'm sure the plow has been knocking it around for years. Sorry for crap pics, it's dark out and don't want to bring it in. Thank you for your thoughts.