In the National Museum of China we find "mirrors" from various Chinese dynasties:
A photo I took of "mirrors" at the National Museum of China in Beijing
Notably, these mirrors are not reflective, the identifying property of mirror. I was thinking maybe they could be laid on the ground and have a reflective liquid added. Or perhaps on the reverse side there was a mirror, but it was not preserved over time.
Question: How do these "mirrors" in the National Museum of China function?