I have a buddy with an old Winchester rifle chambered for that, an 1873 lever action.
He would totally flip over that tool, he reloads his own rounds for it.
Very nice find, Skip.
( If you want to sell it, I want first dibs (depending on price). Would make an awesome Christmas present for him. Right now, the rifle is restored, new Walnut stocks, metal in the white, awaiting a full coverage engraving job he plans to do on it. He is quite the accomplished engraver
www.cdmengraving.com )