ERDL

Engineer Research and Development Laboratory

Developed by the Army Engineer Research and Development Laboratory at Fort Belvoir in 1948, the ERDL camouflage consisted of four colors:

Light Green shade 354
Dark Green shade 355
Brown shade 356
Black shade 357

It was tested alongside the following uniforms at Fort Benning in May 1962:

British green
OG-107 (Olive Green - Shade 107)
OG-107 with load carrying equipment
Marine Corps Mitchell camouflage pattern
Khaki No. 1

The testers all agreed that the ERDL and Mitchell pattern camouflaged uniforms were superior to the solid colored uniforms, with the majority preferring ERDL. The 1948 ERDL pattern was originally designed for verdant terrains in temperate climates and was not therefore optimal for use in tropical environments. However, the test report stated that it did still have advantages over the solid colored OG-107 uniform in such circumstances.¹ Nevertheless, the U.S. Army Vietnam Tropical Combat Uniform board agreed in November 1965 that the standard OG-107 jungle fatigue was preferable for general use in Vietnam.²

However, in December 1965 USARV requested that Natick Labs produce 300 ERDL uniforms for evaluation by specialized units. Reconnaissance platoons from the 101st and 173rd Airborne tested the uniforms during 1966 and reported that there was a definite need for such clothing. As result, in February 1967 USARV filed an ENSURE.³ requirement for 18,373 sets of ERDL camouflage uniforms.⁴

In addition to the Jungle Jacket and Trousers, the Helmet Cover, Boonie Hat, Poncho Liner and Poncho were all eventually made in the ERDL camouflage.

Humphreys, Adolph H. and Gee, David L., Results of User Review of Camouflage For The Individual Combat Soldier In The Field. (U.S. Army Engineer Research and Development Laboratories, Fort Belvoir, Virginia. 9th September 1965)
Summary of Proceedings of United States Army, Vietnam...Tropical Combat Uniform Board. (22 November 1965).
Prior to the widespread introduction of the ERDL camouflage Tropical Combat Uniform, Special Forces and CIDG troops were supplied with Tiger Stripe and Spotted (Beo-Gam) camouflage fatigues by the Counterinsurgency Support Office. Other Army Long Range Reconnaissance forces also wore locally purchased Tiger Stripe clothing.
Expedited Non-Standard Urgent Requirement for Equipment
Support To United States Army In Vietnam - Clothing & Equipment (United States Army Material Command Feb 1967)