From Hoyem 2 p. 33 – “In his book REMINGTON America’s Oldest Gunmaker, author Roy Marcot describes on page 100 the Black Hills Rifle, made only in 1877 and 1878, based on the No. 1 military receiver with 28” barrel, standard sporting stock and fore-end, and chambered for the slightly necked .45-60 cartridge, (shown below). This .45-60 is not related to any other cartridge and was used in no other rifle”. The headstamp matches the cartridge described on p.33 of Hoyem and the dimensions are also the same.