3" X 3 3/4" (74mm X 92mm)

 (dome inkstamp) / N 80

{Zapel Electrical Porcelain}

Picture courtesy Bob Scafe

3 1/8" X 3 3/4" (77mm X 92mm)

 (dome inkstamp) / N 80/2 / 87

{Jedlina Zdrój}

Picture courtesy Bob Scafe