Circular Solution to Saqqara Ostracon

I discovered that the curvature of the Saqqara Ostracon is circular, within small error. This can be seen from the following drawing.

Please note that I used three points to determine the circle; the circle must fit three points. One of those is the assumed point at 140, 0.

I offer no justification for this solution to the mathematical properties. I merely offer it as an interesting solution.