A mission bell is one of the most important factors on a mission. Most missions have one to five bells. Every single mission has at least one of the bells in the facade. Mission bells are usually bronze, even my mission bell is bronze (my mission is called the San Antonio de Padua).
The San Antonio's bell was hung on a mission bell that was hung on a branch of an oak tree that was hanging over the Rio de San Antonio. The other two bells are hung on the facade of the mission. All the bells are covered up today because of burglars attempting to steal them.