Hi Groups, Well, thanks to quick work by Rolynn Prechtl, K7DFW, It is a dog harness mounted radio, used on Scout, Mine Detection, and Tunnel Dogs by the 60th Infantry Scout Dog Platoon in Vietnam. The dog handler wore a PRR 9 helmet mounted receiver. http://www.dtic.mil/dtic/tr/fulltext/u2/869383.pdf Joe Munson WA4VAG