Every once in a while I find a loose primer in some nook or cranny around my bench. About the only way I can come close to telling what kind it is, is by trying to match up the metal and mix color to labeled samples I have put aside in clear coin flips for that purpose. I hate to waste a 3 cent primer so if in doubt, load it up in a mild range load, if really in doubt, make a blank round or throw it away.