This is a Umarex CO2 Pistol known as the XBG chambered in 177BB, model 2254804.
The Umarex XBG has a 19-shot drop-free metal magazine for quick reloading and is powered by a single 12g CO2 capsule. This lightweight" compact BB pistol has fixed front and rear sights and shoots in double action at 410 FPS.
Features:
19-Shot magazine
CO2 Powered
Drop-free metal mag