Natick Labs developed the neckerchief during 1966 after the Tropical Combat Uniform board requested a similar neck scarf to that being used by the Australian forces in Vietnam.1 It measured 36 x 36 inches and was made from OG-107 absorbent knitted cotton. Later in the war it was reduced in size to 36 x 24 inches and was dyed OG-109.
The neckerchief was used mainly to wipe perspiration and mud from the face, neck and hands and was expected to have a lifespan of approximately 6 months. Resourceful soldiers also made their own versions from camouflaged parachute silk.
Interestingly MACV consultant Cresson H. Kearny believed that the experience of jungle soldiers in WWII showed that using sweat rags robbed the body of it's essential natural coolant, tended to spread infection and generally did more harm than good.2
1. Final Report - Tropical Combat Neckerchiefs - ACL-84/67 (Army Concept Team In Vietnam Dec 1966)
2. Jungle Snafus...and Remedies by Cresson H. Kearny (Oregon Institute Of Science And Medicine 1996)