The imagery depicted on this mirror represents the Moon Palace, which is occupied by a hare that pounds the Elixir of Immortality at the foot of the osmanthus tree, and is also inhabited by Chang'e who stole the elixir from her husband Hou Yi. The toad represents the embodiment of Chang'e.
A similar bronze mirror is illustrated by Wang Shilun and Wang Mu in Zhejiang chutu tongjing (Bronze Mirrors Excavated from Zhejiang), Beijing 2006, black and white pl. 117. Another bronze mirror of similar design, but of slightly larger size (13.8 cm.), is in The Metropolitan Museum of Art, acc. no. 25.24 (https://www.metmuseum.org/art/collection/search/61405).