What we know simply as the “Repeater” is really a variation of the Winchester Model 1892, more specifically a modern production called the R92 made by the Brazilian company Rossi. This gun can trace its basic design all the way back to the Henry rifle design of 1860, and saw refinements through the years resulting in it being relabeled as the Model 53 and Model 65. This particular family is specifically designed to fire pistol ammunition, something historically favored as a means of sharing ammunition with a corresponding sidearm.
The name Repeater is a direct nod to the term “repeating rifle,” referring to the design being capable of sustained fire without the need to reload the gun between every shot. This is made possible by an internal magazine which can be loaded through a gate on the side of the frame. By working the lever found ahead of the trigger, a spent round is ejected, a new round is chambered, and the hammer is cocked and ready for another shot — all in one swift motion.
Pictured above is a Rossi R92, but chambered for .44 Magnum rounds that are larger than what we use in-game. It has similar wood furniture, but features a darker finish than our Repeater (which appears to be tarnished steel hardware). Modern calibers also include .357 Magnum, .44-40, and .45 Colt; the original 1892 was chambered in a number of other calibers which are no longer popular in contemporary use.
Image via ZombieHunters.org user TXwaterdog.