I've never seen another one like this. I think this is my favourite find in the pile of insulators purchased at auction recently. It is marked in a circle on the top "AUTOVALVE" and then some lightning bolts, "LIGHTNING ARRESTOR". The words lightning and arrestor are significantly smaller, and also have lightning bolts after them. The shape resembles that of a multipart insulator, as it has skirts or Shells, something I haven't seen on a lightning arrestor. Any thoughts? I shall post another picture of the top so that you may see the embossing.