I can't seem to find anything that matches this insulator. I found it in a antique shop in Ontario. It is an Ohio Brass. 3&1/2 in high, 3&7/8 in width. The crown is very flat as well as the underside of the crown. The neck is very flat as well. There is some staining on the neck but not from wire being tied more so from a clamp. It is light gray in colour. Any idea what U number this might be? Thanks Brian