3 3/4" X 4" (94mm X 103mm)

(ear top incuse)

{Rheinisch-Westfalische Isolatorenwerke}

Picture courtesy Bob Berry

3 3/4" X 4 1/8" (96mm X 106mm)

(ear top incuse)

{Berghaus}

Picture courtesy Connie Dueker

3 3/4" X 4" (96mm X 103mm)

(ear top incuse)

{Wesselwerk Bonn}

Picture courtesy Bob Berry