This is one of only an estimated fifteen, possibly as many as twenty, .30 caliber Trapdoor rifles manufactured by Springfield Armory between 1890-1892 for the purpose of experimenting with various smokeless powders, testing velocities, studying ballistics, and performing pressure tests in the development of a new .30 caliber (.30 Army) smokeless powder cartridge. The Chief of U.S. Ordnance directed Frankford Arsenal and Springfield Armory to work together in the development of a new rifle using a new small caliber smokeless powder cartridge. The test rifle chosen was the standard U.S. Springfield Trapdoor rifle; however, the standard issue Trapdoor receiver of the time was deemed too weak to handle the higher pressures generated by smokeless powders. Springfield embarked on a massive redesign of the receiver to accommodate this development work. Testing of the smokeless .30 caliber Trapdoors started in 1890, and various ammunition and ballistics tests with at least ten of these rifles continued as late as 1895. These rifles were all considered as experimental models and went through numerous design and engineering changes to be able to accommodate the new improved high velocity smokeless powder cartridges, with each individual rifle in some instances being somewhat different. Since they were all experimental, they were never serial numbered, but instead were tracked by a small capital letter stamped on top of the breech of the barrel. The letters ran from "A" through "T", as mentioned in the 1894 Report of the Chief of Ordnance, along with additional barrels for these rifles manufactured with varying designs and steels. Rock Island Auction Company previously sold rifles with letters "E" and "I". Only a select few of these extremely rare rifles survive today, with this highly attractive example, letter "H", very likely the finest condition survivor. These rifles are extensively written up on pages 199-212 of the book "The 45-70 Springfield" by Frasca & Hill, with information also on pages 289-292 of "The 45-70 Springfield Book II". Features include a reinforced no-arch breechblock with the positive cam/locking latch, small tip firing pin, redesigned extractor intended for the new rimmed cartridge, the correct, reinforced straight sided receiver that measures 1 1/8 inch across the width of the receiver, with side walls, that measures approximately 1/4 inch thick on each side, with the matching positive cam/locking latch cutout, completely redesigned one-piece trigger guard with the long swivel on the upper front edge of the trigger guard bow, and new redesigned stock intended for the smaller diameter barrel, with a boxed script "SWP/1892" (Samuel W. Porter) inspection cartouche stamped on the left wrist of the stock and a circled "P" proof behind the lower tang. Pinned blade front sight and prototype Buffington rear sight with no graduations on the ladder. According to Frasca's book at the time of writing (not including this rifle in his count), "Nine of the original fifteen rifles are known today, four in museums and five in private collections." These extremely rare rifles played an important role in the evolutionary development of the .30 caliber smokeless powder cartridge in U.S. military service.