The can opener is approximately long, and consists of a short rectangular metal handle with a small, hinged metal tooth that folds out to pierce the can lid. A notch just below the hinge keeps the opener hooked beneath the rim of the can as the device is "walked" around to cut the lid out. A larger version called the P-51 is somewhat easier to operate thanks to the greater leverage it can generate. The designer of the original device that acquired the official U.S. military designations "U.S. ARMY POCKET CAN OPENER" and "OPENER, CAN, HAND, FOLDING, TYPE I", commonly known as the P-38 is unknown. In spite of widespread claims that the P-38 was designed in a 30-day whirl of inspired effort by the U.S. Army Subsistence Lab in Chicago in 1941, a fully fledged version of the device (differing only in the hole for attaching to a lanyard being on the opposite end of its body) appeared in a 1924 edition of
Popular Mechanics. It is described as being "designed for campers and Boy Scouts", and is illustrated in use. Readers were offered more information on the item by writing to Popular Mechanics, Chicago. The P-38 was preceded in US military
field rations such as the
K-ration and
C-ration by then traditional
twist-key can opening, where a provided key was inserted in a tab and twisted around a can to peel away a metal sealing strip. P-38s are no longer used for individual rations by the U.S. military, as canned C-rations were replaced by
MRE rations in the 1980s, packed in plastic pouches. The P-51, larger at , is included with United States military "Tray Rations" (canned bulk meals). P-38s are also still seen in disaster recovery efforts and have been handed out alongside canned food by rescue organizations in several countries. J. W. Speaker Corporation of
Germantown, Wisconsin, was one of the early contractors for the military P-38, producing them in the millions (stamped "Speaker USA"). The opener was also manufactured by Washburn Corporation (marked "US Androck"); and later by Mallin Shelby Hardware inc (closed 1973) of
Shelby, Ohio, variously stamped "US Mallin Shelby O." or "U.S. Shelby Co." ==Operation==