Anybody ever heard of this one that recently showed up on ammoguidedotcom ?
"This obscure round was introduced in 1880 during the heyday of long-range competition shooting in America. Period blackpowder rounds targeting this market tended to fall into two styles: straight-walled and necked cases. This was obviously a member of the latter.
"The .45-100 Remington seems to be a larger version of the successful .44-90 Remington Special released almost a decade earlier. Available as a special order chambering for Sharps and other rifles, no other cartridge dimensions are compatible. The cartridge was dropped from catalogs within a few years."