DE-10 Pistol is a type of pistol. DE-10 Pistol barrels are looted from Death Watch NPCs in the DWB, and are used in the crafting of DE-10 Pistols. These are made from a looted schematic, from Black Sun and Death Watch NPCs or from loot bins. As of Chapter 3.7 DE-10 Pistol barrels are dropping once more with serials, so newly looted barrels can be used in the crafting. For a while DE-10 Pistol barrels were dropping without serials, thus making them un-usable in the crafting of a DE-10. If you have one of these barrels, Customer Services will trade you it for a barrel that has a serial number.