I got this U-39 Fred Locke pony at the KC National. I noticed it has a dark spot on the skirt resembling a burn mark, with a pit in the center of the dark area. At first I thought it might be an electrical puncture like I've seen on a few old low-quality Pittsburg distribution styles.

But I noticed this mark is different. The pit is NOT a hole all the way through the insulator, and everything inside the pinhole and skirt look fine. I wouldn't expect a telephone line to have enough "juice" to puncture an insulator -- unless, I suppose, this little telephone pony got pressed into service on an electrical line at a much higher voltage than it was designed for.

Just a wild guess on my part – during manufacture, some bit of combustible matter stuck to the glaze (maybe a crumb of the glaze guy's lunch!) and burned off in the kiln, leaving this black mark and little pit?

Anyone with more knowledge of porcelain manufacturing have any ideas?