"Designed to be small, easily carried and mistaken as a pocket watch, the Expo Watch camera was a popular novelty, or disguised camera, of the early 1900s. The camera measures 2 1/8 x 7/8 inches and weighs 2 3/4 ounces. The Expo camera was available for over 3 decades. It was introduced in the United States in 1905 and offered for sale as late as 1939.
This view shows the "watch winding stem" which is actually the camera's lens mount. Right of, and above the stem, a round button protrudes from the side of the casing. This is the shutter release. A slot with a protruding metal tab can be seen further right and mid-body in this photo. Pulled half-way along the slot, the tab opens the shutter for time exposures. Pulling the tab fully along the slot arms the shutter for instantaneous shots."