If you guessed a Japanese coin on Tuesday, then you are correct! This shiny piece is a Japanese Bunkyuu Eihou 4-mon coin, though our coin wasn’t always so shiny. It took some conservation effort to bring it back to the pictured condition. As a rule of thumb in conservation, the ideal method in cleaning an artifact is to approach it with the least invasive cleaning technique. The coin was soaked in a container of distilled water for two weeks, allowing the encrusted material to loosen up. Then the rest was up to the handiwork of the Dremmel tool, which was carefully used to scrub off the black encrusted layer.
The 4-mon coin was in circulation throughout Japan for a good 200 years with some minimal changes, but in 1863 the Tokugawa Shogunate government issued a change in the characters on the coin which roughly translates to “eternal currency of the Bunkyuu Era”. However, the government collapsed in 1867 along with the currency. This event marked the end of the feudal military government and the beginning of the restoration of imperial rule – unlucky for the Tokugawa Shogunate, but fortunately for us it indicates a small window of time that this coin could have been in circulation.