The K-22 was S&W's first model to offer a recessed cylinder sometime around 1931 IIRC ,
The second was the .357 magnum around 1935.
Only the 22 caliber and Magnum handguns had this feature until the early 80's when it was deleted in the non rimfire Magnum handguns to save production time and costs, S&W rimfires are still recessed.

The pinned barrel was deleted also to save production time and money although many transitional guns are found with recessed cylinders and non pinned barrels probably until the supply of recessed cylinders ran out.