An antique kerosene-powered signal lantern from the early 20th century. Historical use: These lanterns were used for long-distance optical communication, often using Morse code. Mechanism: The lantern uses a kerosene flame as a light source, protected within a durable metal casing. Design: Includes a focusing lens (prism) on the front to focus the light beam in a specific direction. The signal lantern was an important means of communication before the age of radio.