Tracking down the correct James TAMS (I'm descended from one who married Jane AMISON) could be challenging. I have come across at least three sets of James TAMS's, all with a son James. There may be more.
One question though, was the piece of pottery in question made in England, or in the USA (ie Trenton, NJ?)There is a pottery exhibit in the NJ State Museum. Perhaps I could look into that, as I always pass it on the way to our State Archives.