Korea - 100 Mun, 1866 - 1867

I'm thinking this one is authentic.
39.8 mm; 22.9 gm. Shows some cast filling on one character. Ones with wear patterns like this (center hole rounded and circular scratches) were used as spacers or washers between grain grinding stones.
This is a One Hundred Mun ("Value Hundred" tangbaekchon or dangbaekjun [sang pyong tong bo] coin. In this photo has the Obverse/Reverse images are flipped.

Sang P'yong T'ong Bo, Hojo Treasury Department
Korea, ca 1866. Obverse Image: Four Chinese characters read top, bottom, right, left Obverse Text: Romanization: SANG / P'YONG / T'ONG / BO (Translation: Always Even Currency). Reverse Image: Character for Hojo Treasury Department at top, denomination read right, left, bottom. Reverse Text: Romanization: HO / TANG / BAE / CHON (Translation: Character for Hojo Treasury Department, worth one hundred).
The One Hundred Mun is the only denomination of sang pyong tong bo coinage for which accurate mint records exist. These coins were first cast by the Treasury Department on December 12, 1866 and put into circulation beginning January 15, 1867. The last coin was produced on June 16, 1867 which means these coins were cast for only 172 days. A total of 1,784,038 "One Hundred Mun" coins were cast by the government.
In general the One Hundred Mun coins minted by the government have a diameter of 40.6 mm, a thickness of 2.8 mm and a weight of 25.1 grams. There are about 50 varieties of the 100 Mun coins with differences so slight (character stroke style, size, etc) it is hard for a Westerner to discern. See my other examples here in the Moneta Museum.

VIEW & DOWNLOAD Korean Coin and Charm Articles:
A Survey of Korean Coins - Joseph E. Boling: [ link ]
Korean Charms and Amulets - Starr
[ link ]
German Coin Techniques in Korea - Won Yu-Han
[ link ]
Rulers of Korea
[ link ]
Picture Album of 100 Korean Amulets
[ link ]