2 1/8" X 3 1/8" (54mm X 79mm)

No markings

Picture courtesy Bob Berry

2 1/8" X 3 1/8" (54mm X 79mm)

(dome embossed)

                              PN-T-400

Picture courtesy Bob Berry

2 1/8" X 3 1/8" (54mm X 79mm)

(dome) IŁ ITS-3

Picture courtesy Bob Berry

2 1/8" X 3 1/8" (54mm X 79mm)

(dome) IŁ ITS-3

Picture courtesy Mike Green

2 1/8" X 3 1/8" (54mm X 79mm)

No markings

Picture courtesy Bob Berry