 It was designed for the U.S. Navy as a large-capacity version of the S&W Model 39, the basis of their Mark 22 "Mark 22 Hush Puppy" suppressed pistol.In 1965, the U.S. Navy commissioned a version of the S&W Model 39 that could take the 13-round magazine of the Browning Hi-Power.In early 1970, a dozen experimental all-stainless-steel prototypes were made and were issued to Navy SEAL commandos for evaluation in the field.