Mahogany plate holder for half-plate size camera. Unexposed plates were mounted in such light-tight holders and inserted into the camera to make an exposure.
The rectangular wooden frame opens like a clam, held closed by two brass clips. When opened two glass photographic plates may be loaded. There is a wooden slide each side of the frame. When the frame is inserted in the camera, a wooden slide is withdrawn to expose the plate, and slid back in when the frame is removed from the camera. The frame may then be turned over and reinserted to expose the second plate.
The assembly was then removed and used to store the exposed plate until it could be developed.