1835-1870 Japan 100 Mon oval coin 100 Mon Tenpōtsūhō

Circulated coin as seen here.

Obverse

Four vertical characters divided by hole

Lettering:

天

保

通

寶

Translation: Tenpo Currency

Reverse

Value above hole and signature of the mint official below

Lettering:

當

百

Translation: Equal Hundred

Edge

Smooth, paulownia stamps on the left and right side (various sizes and forms exist)

Coin Specifications

Issuer: Japan

Emperor: Ninkō (1817-1846)

Years: 1835-1870

Value : 100 Mon = 1⁄40 Ryō

Composition: Bronze (Cu 78%, Pb 12%, Sn 10%)

Weight: 20.7 g

Diameter: 49 mm

Thickness: 2.6 mm

Shape: Oval (With a square hole)