This one makes me a little sad. It's probably the coolest thing I'll ever own, it's all down hill from here, I'm not sure what I'll do with the rest of my life, maybe take up nitting? No point looking for something better than this.
This is a Japanese Edo period 1 ryo koban. This is the unit of account for Samurai, Daimyo and merchants. Because the Shogun was in a contestant power struggle with the Daimyo and couldn't easily tax them they debased the currency with increasing amounts of silver. By 1819 when this koban was minted it was almost half silver, by the beginning of the Meiji period it was as low as 23% in some cases. This coin/ingot could have bought roughly 40 nice meals in an inn or 1 koku which was notionally enough rice to feed a man for a year (around 150kg), this was the way that local lords would measure the productivity of their lands and pay their samurai.
This koban might have been used to pay a ninja to assassinate a local feif or as part retainer for a low level samurai. It might have been held in the treasury of the shogun or given as a devotional item to a temple.
It's around 6cm long and came with a great authenticity certificate folder from JNDA which describes it and has a pictures of the obverse and reverse in it.
It was a little over spot but
totally worth it.
http://s22.postimg.org/fmr5exuwh/20150815_160824.jpg
http://s14.postimg.org/3u5shg7yp/20150815_160844.jpg
http://s11.postimg.org/4ldybkblf/20150815_161030.jpg
Actually, in doing a bit of research for this post I came across something even cooler, so I still have a goal! An oban is worth 10 ryo which is roughly 10 times bigger than my koban. They're about 16cm tall and text on the front reads 10 ryo. Because you had to pay a fee to have the calligraphic wiring on the front re-done if it rubbed off they were generally pretty well looked after apparently. Unfortunately they seem to go for pretty penny, it's going to take all my powers of bargain hunting to get one of these.
https://upload.wikimedia.org/wikipedia/commons/4/4d/Keicho_Oban_1601.jpg