The Colt 6520 10mm autoloading pistol is a highly durable and efficient weapon developed by Colt Firearms prior to the Great War. It proved to be resistant to the desert-like conditions of the post-nuclear wasteland and is a fine example of workmanship and quality construction (at least for the pre-War models, which became more scarce over time). The simple design of the gun allows it to be easily manufactured with relatively basic equipment, making it possible to be replicated in workshops in the post-nuclear world.
Unlike the standard classic 10mm pistol, Ultimatum possesses a black finish and intricate engravings, including Gunners iconography, deathclaws, radiation symbols, an image of the Sole Survivor, and two written passages on either side of the barrel. In addition, it cannot be equipped with barrel modifications.
By default, it carries the long barrel, glow sights, survivor's grip and muzzle brake modifications. It possesses the "Irradiated" Legendary effect, adding 50 radiation damage to every shot.