I recently added to my small collection of polygraph memorabilia the Department of Defense Polygraph Institute (http://www.dodpi.army.mil) (DoDPI) challenge coin pictured below. Actual size is the same as that of the old silver dollar (~1.5" diameter):
(https://antipolygraph.org/graphics/dodpi-challenge-coin-obverse.jpg) (https://antipolygraph.org/graphics/dodpi-challenge-coin-reverse.jpg)
This joins an AFOSI Polygraph (https://antipolygraph.org/forum/index.php?topic=470.msg2229#msg2229) challenge coin as the second in my collection.
Which side does it land on for "DI". lol-how funny that polygraphers would give out coins.