Thomas U-18 porcelain insulator with interesting spots

By Dale Nielson; posted May 19, 2017

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I recently acquired this U-18 insulator that has approximately 70 spots on the outer skirt. The blue-black spots are slightly depressed and have light orange halo's around them. I've seen this same effect on old glazed clay marbles and occasionally on small sections of brown glazed wall tubes. The insulator is a MLOD, dry process, carved top Thomas.