Here's an interesting piece that I found in a box of insulators a few years back. It was found in a town that had a large brick factory a hundred years back. It is marked " AL 1900 ". It is either Little Alvin's kindergarten project or somebody needed an insulator and found it easier to make one at work than to shell out 8 cents at the hardware store. (Any other ideas?). It has a waxy parafin like glaze.