To date, these 2 culprits have managed to avoid being identified. Other than height and width, virtually nothing is known about them presently. There are no other markings to further assist in identifying them, although they are believed to be European in origin because of the better quality glazes. While both insulators are 2-3/4 inches wide at the base, their heights differ as indicated. If you have any suggestions where these insulators were made or used, I would appreciate hearing from you. Please note, the right hand insulator has a top groove, the left hand insulator is flat, no top groove. Thanks for looking