This pistol paper model is a Hellsing ARMS .454 Casull Auto (shortenedto Casull), a semi-automatic handgun that is one of Alucard's favorite weapons of choice, based on the anime and manga series Hellsing, the papercraft was created by [Ramona] Yummei Karasu & Hoborginc. The engraving on the frame of the gun (Hellsing ARMS 000001) indicates that it is the first custom weapon ever made by Walter C. Dornez.
The Casull is a classical semiautomatic handgun, based on pre WWII handgun designs by Colt, most notably Colt's popular handguns, the M1911 and the M1903. It weighs approximately 6 kg unloaded and has a magazine capacity of six .454 Casull cartridges.
The overall design of the Casull is simple, using the Browning short recoil mechanism. Its most recognizable feature is its long slide, counteracting the weapon's heavy recoil with its weight. The barrel is 10 inches long and finished with titanium nitride which gives it a characteristic gold color. [Source: wikia]
You can download this papercraft model here: Hellsing ARMS .454 Casull Auto Pistol Paper Model Free Template Download