Hello All,

I've found a few examples of a ceramic artifact type in the collection of a California historic house museum, and I can't figure out what they are.

The objects are circular white earthenware discs, glazed and undecorated, between 6" and 8" in diameter, with what appears to be a footring, and with a single approximately 1/2" hole in the center of each. The hole was cut before glazing. 

A picture can be viewed here: https://dl.dropboxusercontent.com/u/13574856/Ceramic_Artifact.jpg (this photo is of two of the objects stacked on top of one another).

I'd appreciate the input of anyone knows this artifact.

Thanks,
Stacy Kozakavich
Oakland, CA