Other insurgency weapons may be sanitized versions of traditional infantry or defensive weapons. These may be purpose-made without markings, or they may be standard commercial or military arms that have been altered to remove the manufacturers markings. Due to the covert nature of insurgency weapons, documenting their history is often difficult. Those that can legally be traded on the civilian market, like the Liberator pistol, will often command high prices; although millions of the pistols were made, few survived the war. These examples are all arms that were either used as insurgency weapons or designed for such use. Purpose-built weapons were designed from the start to be used primarily for insurgent use, and are fairly crude, very inexpensive, and simple to operate; many were packaged with instructions targeted to speakers of certain languages, or pictorial instructions usable by illiterate users or speakers of any language. Dual-use weapons are those that were designed with special allowances for use by insurgent troops. Sanitized weapons are any arms that have been manufactured or altered to remove markings that indicate the point of origin. IEDs are improvised explosive devices. The FP-45 Liberator was a single-shot .45 ACP derringer-type pistol, made by the U.S. during World War II. It was made from stamped steel with an unrifled barrel. The designation "FP" stood for "flare projector", which was apparently an attempt to disguise the use of its intended purpose by obscuring the nature of the project. It was packed with ten rounds of ammunition and was intended to be used for assassinating enemy soldiers so that their weapons could then be captured and used by the insurgents. The instructions were pictorial, so that the gun could be distributed in any theatre of war, and used even by illiterate operators. The country in which the largest quantity was used was the Philippines. The CIA Deer gun was a single-shot 9×19 mm Parabellum pistol, made by the U.S. during the Vietnam War. It was packaged with three rounds of ammunition in the grip and packed with instructions in a plastic box. If air-dropped into water, the plastic box containing the pistol would float. Like the earlier FP-45 Liberator, it was designed primarily for assassination of enemy soldiers, with the intention that it would be replaced by an enemy soldier's left-over equipment. The instructions for the Deer Gun were pictorial, with text in Vietnamese. Although various submachine guns were