Looks like a divining pendulum. Could be one of the few the US Army experimented with in the 70's. Soldiers were sought out for their aptitude and tested for 'psychic' powers. They were given a map and a pendulum and told to locate VC tunnels in Vietnam. The Pendulum would hang from the soldier's hand and gravitate toward tunnel entrances- supposedly. I must assume we abandoned the divining pendulum for more practical techniques, like satellites, dogs, a pair of eyes, or even a newspaper.