W. M. Co Semi Porcelain Back Stamp
I have a pitcher and wash bowl by the Willets Manufacturing Co of Trenton NJ. I know it dates between 1879 - 1909, but I would like to be more specific on the date period. They used a few different stamps, and this is the one in the octagon (W. M. Co ) with Semi above and Porcelain below. It's the only one that I haven't been able to put a time period to.
Anyone here have info on the dates Willets used the octagon shape back stamp?