At least it is new to me.
Circle - small - 16 indents???
Burt Co chip. It is a clay compression chip so has to be made pre 1988 and could be much older.
The circle is much smaller than any of the other circle molds, I have.
There are 16 strange indents inside the circle. They range from large to small in an even manner. I feel certain they were put there in the molding process.

This is the 121 mold in my mold file.