This is a Ruger 22/45 Mark III 22LR Target Rimfire Pistol 5.5-inch barrel with Molded Grips. 

No other .22 LR pistol provides the feel of the classic 1911 pistol with the proven reliability and value of the Ruger® 22/45™ pistols. The perfect trainer, it allows for low-cost practice and provides shooters with the familiar and preferred grip shape and feel of the famous 1911 .45 caliber pistol.

In addition to the identical grip angles, the 22/45 features the same fire control locations (manual safeties, magazine releases and bolt hold-opens) as the 1911, making them perfect for .45 caliber shooters looking for an affordable way to train. Also perfect for plinking, target shooting, and small game hunting, the 22/45 is available in a variety of configurations and barrel lengths, each with the same trusted reliability that Ruger has delivered since 1949.