For surplus cases I look for primer pockets that have not been reamed yet, this will let you know that they have only been shot once. If they have been reamed, I look at the condition of the case, if the mouth still has good thickness to it, good sholders and not alot of resizeing marks down the case Ill use them, other than that its a crap shoot! Most of the time Ill buy virgin brass and keep up with the amount of times its reloaded.