2 3/8" X 3" (58mm X 73mm)

No markings

{New Zealand Insulators}

Picture courtesy Bob Berry

2 3/8" X 3" (58mm X 73mm)

(dome incuse) NZI 

{New Zealand Insulators}

Picture courtesy Bob Berry

2 3/8" X 2 7/8" (58mm X 70mm)

(dome incuse) NZ / I in a circle 

{New Zealand Insulators}

Picture courtesy Bob Scafe