2 7/8" X 3 1/8" (73mm X 79mm)   No markings   Picture courtesy Jack Nesbit

2 3/4" X 3 1/4" (70mm X 82mm)   No markings   Picture courtesy Jack Nesbit

Recovered from a telegraph line running between the Attadale house to Bendronaig lodge (Scotland).

U number assignment from Worldwide Porcelain Insulators by Marilyn Albers & Jack Tod.