Extremely rare jungle sensor disguised as a moss covered stick, supplied by the CIA and placed by Special Forces teams and LRRP/Rangers along suspected enemy infiltration routes these came in three different designs, a stone or pebble was one other version. As you can see three unissued sensors still on the original plastic covered card from which they would of been issued. The card held ten sensors and each one had a perforated edge around it so you could tear each one off of the card individually. This card is dated 1970 but from a 1969 contract.
Scattered Shots 
What did the sensor do exactly? I assume monitor for sound or vibration, communicate via radio? Always been fascinated with the Vietnam-era technology. I believe the Son Tay raid used some very early unmanned drone flights for reconnaissance/surveillance data gathering prior to the raid. Difficult to find much info about this, though.
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They had senors to measure thing you wouldn’t believe possible back then. Some could detect ammonia from piss in areas to detect troop concentrations, some for vibration, sound, fecal matter et. They even drop chemicals on the Ho Chi Minh trail to turn the dirt into an impassable mud. It’s a huge topic. Vietnam really was a proving ground for a lot of ideas and tech that sounds from a comic book or James Bond movie,
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If you know of any good books or references on this stuff, send them my way.
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I don’t know of any that focus on that sort of thing in any detail. If you find one, let me know as well
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Especially the ammonia sensors. I know they counted latrines to estimate Japanese force sizes in WW2, but direct piss measurement is next level.
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