This pistol can be used either as a semi-automatic pistol, or can be single shot by tipping the barrel. It comes in .25 ACP (M950) or .22 Short (M950B). With a long barrel it is called "Special." It was introduced in 1950, and is available in a variety of finishes as well as engraved.
Measuring right panel vertically: 2 7/16" long x 1 1/2" wide (about 1/8" down from curved corners at top)
