After some research i think this mold is for a Black Powder Cartridge Rifle like the 50-70 with the 515 being the Diameter? And the 2 grooves are Crimp grooves. It sure looks like my TC Molds
This was written by Louie Bartolomeo as an Ebay buyers guide for TC Molds
1. T/C DID NOT MAKE A 58 CAL MAXI HUNTER MOULD FOR SALE, BUT THEY DO SELL THE CAST BULLETS.
2. T/C MOULDS WERE MADE FOR A SHORT TIME THROUGH BY SHILOH, UNTIL BUSINESS PROBLEMS BETWEEN T/C AND SHILOH ERUPTED.
3. T/C ALSO HAD FOR A EXTREMELY SHORT PERIOD OHAUS PRODUCE MOULDS FOR THEM.
3. T/C WOULD PUT NEW LABELS OVER OLD ONES ON THE MOULD BOXES WHEN THEY NEEDED TO. SO SOME OF THE BOXES HAVE A LABEL UNDER, CAREFULLY REMOVING THE TOP LABEL SOMETIMES REVEALS RARE EARLY BOXES OR MISPRINTS.
4. T/C MOULD HANDLES ORIGINALLY HAD BRASS FINISHES, WHICH USUALLY WORE AWAY EASILY. NEW HANDLES WITH BRASS ARE RARE.
5. OLD SHILOH MOULDS AND HANDLES WILL INTERCHANGE WITH T/C MOULDS AND HANDLES.
Here is an old post i dug up, this guy claims that Green Mountain made molds for TC as well? Back in my TC Maxi Mold buying spree, and LOTS of research, I don’t remember anything mentioned about Green Mountain making Molds for TC?
Thompson Center marketed molds under their (TC's) brand name, but had them produced by others: Green Mt., Lyman, Ohaus, and maybe Shiloh. The only distinguishing feature is the shape of the sprue cutter such that the Green Mt. and Ohaus ones look exactly like the TC's (long, "squared" end) with the Lyman's being shorter with a round end. Shiloh, OTOH, I can't say. Btw, I sold a Green Mt. .50cal. RB mold (iron) and an Ohaus .440" (iron) RB mold last year. Both looked exactly like the TC "product."