The “Bronze Cannon” of Osaka Castle is a cannon used for time signals, which was popularly known by citizens as the “Don of the Castle” or “Don of Ogo”. This cannon was manufactured in 1863 by Seijiro Momose and others, founders of the Mimasaka Tsuyama Domain (present-day Tsuyama City, Okayama Prefecture), by order of the shogunate, and was originally installed in the Osaka Tempozan Battery. After the Meiji Restoration, it was moved to Osaka Castle and used as a signal gun to announce the time from 1870 (Meiji 3). Initially, the gun was fired three times a day, but after 1874, it was fired only once at noon, and its sound echoed throughout the city. However, due to gunpowder saving and other reasons, it was discontinued around 1924. The cannon is now on display near the entrance to the Osaka Castle Keep.