The most typical mule ear pill lock was patented in 1830 by Ephraim Gilbert of Rochester, NY. He sold the right to make these locks to other NY State gunmakers . Several are illustrated in Swinney's " New York State Firearms Trade". Swinney also illustrates an original can of pill lock pellets with the note that the fulminate was rolled in bees wax to keep the pellet together and help prevent the pill from falling out of the gun's vent. The pill lock gun in my collection is a Billinghurst mule ear over under .