This type of sundial, also known as a diptych dial because of its 2 hinged faces, shows the hour lines of a horizontal dial and a vertical dial. A list of 42 key locations around the world is inserted into the top cover, with their corresponding latitude given to the nearest degree.
This type of diptych dial was very common, in particular in Germany during the 16th and 17th centuries. They were usually made of gilded copper and ivory, but could be made from other materials such as wood, paper, silver, or gold.
This object is signed by J. Kleininger, a German instrument-maker from the second half of the 18th century.