First let me say that my casting skills are basic. I do OK with bullets for my 45/70. I Recently acquired two Ideal 4 cavity molds. One is marked 312521, 138gn and the other is marked 350522. The box for the 350522 is marked 348? Both molds are also marked "Harvey Prot-X Bore". I searched this on the site and found a number of old posts about Harvey Prot-X Bore, but nothing on those two mold numbers. I sort-of understand but neither of these molds have any way of attaching a zinc washer. They are smooth sided round nose cavities. Can any give me an idea of what these are?