I have a folembray glass insulator that my father in law found in Norway back in 1981. It has the number 5554 on the back and folembray on the front. It also has what appears to be a crack on the interior of the glass..although you cannot feel any kind of a crack. I havent been able to find any pics or info on it. Or what its value may be. Any knowledge or suggestions? Thannks...