U-2920: England
4 1/2" X 4 1/8" (110mm X 101mm)
(dome side)
Picture courtesy Bob Berry |
Note this is a two part insulator with the base being an oil cup designed to increase the insulation value when filled with insulating oil. G & G stands for Gaskell and Grocett.
U number assignment from Worldwide Porcelain Insulators 1986 Supplement by Marilyn Albers & Jack Tod.