A most unusual insulator to say the least. This Hemingray 19 has a six sided nut with machine threading embedded in the dome. It also has a metal insert in the threads. It looks like the glass is crackled around the nut. I imagine this would be common, metal against glass. There are just a couple of flakes off the base of the skirt by the 19. Otherwise the insulator appears to be in great shape. I have priced this rare piece way below the price guide. $500....I pay the shipping but you have to buy the insurance ($6.50)