Japan - Koshu Ichi-Bu Kin type - FAKE

I initially thought this was some kind of 'coin weight' from China. In fact, you may find this listed elsewhere in the Museum as that, although I couldn't find it. Then I came upon a listing for this type of coin under Japan Provincial coinage for Koshu. The problem is, while they look just like this coin, all are made of gold and this clearly looks like brass. In the west (see Italy 20 Lire coin weight), brass look alikes are known to be used as 'coin weights' to confirm gold coins on a balance scale. See KM's SCWC for the wide variety of these coins in many different weights of gold. This appears to be like the ICHI-BU KIN (one Bu Gold) shown in KM. The diameter is about right but the gold weight should be 3.70 - 4.0 gram (14-17 mm), while this brass copy is 15.5 mm and weighs only 2.43 g., so it wouldn't make a good coin weight for any of the types shown in KM. It's a obvious fake! But what follows is a fascinating history of these coins:
Takeda Shingen’s Koshu-Kin Coins、
Koshu-kin (Koshu Gold) was Japan’s first systematic gold coinage to be minted. Cast until the Edo Period Bunsei era (1804-1829) the coins were originally circulated through Takeda Shingen’s province of Kai (Yamanashi).
Around the edge of the coins were small raised dots, giving the impression of the nail studs holding the stretched skins across a Taiko drum, and for this reason, they were also known as taikoban. These were difficult to forge, and hence coined the phrase (pun intended!) “Taiko-ban o-su”, meaning “undeniably”, or “Without a doubt”.　Modern day 500 Yen coins feature the same denticles around the outer rim.
Although the actual origin of the Koshu Gold is unknown, it is believed the coins were minted by four families using gold taken from Kai provinces deep mines.
The coins were apparently first used by Takeda Shingen to pay for a manuscript of the Tale of Genji, with remaining records showing that he paid 5 of the cold coins for the exchange.