Here is one of the Medalta company stamps on the inside and under the glaze of a Medalta type insulator. I have never heard of another Medalta style insulator having a stamp in it, have you?. Several years ago at a Tom Bond Insulator Show, Robin Harrison tried to get a picture of this insulator with the stamp showing. I forgot, and never heard anything further about it. I can still see Ryan Paton holding the insulator while Robin tried to get the angle just right so that the stamp showed. Today, the lighting was perfect and here is the result. There are books showing all the Medalta logo stamps used over the years. I wasn't smart enough to note which stamp it is. Too late smart. You can see this insulator at the Merritt Insulator Show, Sept. 9-10, 2006