1 5/8" X 2 1/8" (42mm X 55mm)

(dome recess embossed) CN2

Picture courtesy Dave Dangora

1 1/2" X 2 1/8" (39mm X 55mm)

No markings

Picture courtesy Bob Berry

1 1/2" X 2" (39mm X 53mm)

No markings

{older style - crude}

Picture courtesy Dave Dangora