The Model 27 pump action was made from 1909-1911, the Model 27S from 1913-1932. This style of rifle was called "trombone" or "slide" action.
First introduced with an octagon barrel in .25-20 and .32-20, improved (27S) in 1913 with the addition of round and octagon barrel variations which were chambered for the .25 rimfire cartridge. PGW carries only the stock for this rifle (one universal style fits both models).