I was given some Lee round ball molds, all seem to be pretty straight forward as to what caliber muzzleloader they were designed for, except one. The mold in question is a single cavity round ball mold with Lee's parts number 90413. The number, and measurement seem to indicate that this mold throws a .413 round ball. I can't imagine what modern muzzleloader was produced in large enough quantities in .42 caliber for Lee to put such a mold into production. It might also be the reason the mold look unused.
Hungry Horse