This pair of "clickers" was a recent find. They were made in Hong Kong and probably date to the 1970's.
"Clicker" toys have been around since the late 1800's. The simplest form is constructed from two pieces of opposing tin with a spring loaded between them. Squeezing the two pieces of tin together causes one piece to distort. Releasing the pressure, the tin returns to it's original shape causing a loud pop. "Clickers" were even used during the D-Day operation of World War II. The 101st Airborne Paratroopers used them to locate and identify their comrades after landing. Unfortunately, some German troops became keen to this and began emulating the sound with their rifles, drawing the Allies out into the open where they were shot on sight.