It depends on where you found it. In the woods, squirrels and rabbits, and depending on the locale, porkies chew them fast. Out in a field they sometimes dont meet those critters and last a long time, especially the further west you are. If, when you pick it up, one side is bleached and the other side has color, its old. If the base under the rosette still has the grey skin ring, the blastema scar, its likely not that old.