First authorized for Limited Production procurement in 1966, the plastic machete sheath featured a built in sharpener and thirteen 2mm ventilation holes. The plastic sheath was thought to be superior to the cotton duck model because it did not stiffen or crack in cold climates.1 However, in Vietnam's humid jungle environment the plastic sheath's ventilation was inadequate and the machete blade soon rusted as a result.2
1. Procurement Instrument Release Forecast Volume II (US Army Natick Laboratories May 1966)
2. Jungle Snafus...and Remedies by Cresson H. Kearny (Oregon Institute Of Science And Medicine 1996)