2 3/8" X 3 5/8" (58mm X 89mm)

(skirt inkstamp) Z "in a circle" / 55

                         MADE IN JAPAN

{Maker unknown}

Picture courtesy Bob Scafe

2 3/8" X 3 5/8" (58mm X 89mm)

(skirt inkstamp) 48 / NATIONAL

                         MADE IN JAPAN

{Maker unknown} 

Picture courtesy Bob Scafe

2 3/8" X 3 5/8" (58mm X 89mm)

(skirt inkstamp)

{Maker unknown}

Picture courtesy Bob Berry

2 3/8" X 3 5/8" (58mm X 89mm)

(skirt inkstamp)

{Maker unknown}

Picture courtesy Bob Berry

2 3/8" X 3 5/8" (58mm X 89mm)

(skirt inkstamp) 48

                         MADE IN JAPAN

                          National

{Maker unknown}

Picture courtesy Craig Polkinghorne

2 3/8" X 3 5/8" (58mm X 89mm)

(skirt inkstamp)

                         49

                         MADE IN JAPAN

{NGK}

Picture courtesy Craig Polkinghorne