Aluminum Copper plated aluminum coin
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3D3DCopper plated aluminum coin.
I got this coin on a trip to Japan last year, and only now got around to photographing and describing it. Japanese one-yen coins are aluminum, but they are undisguised. This one, whose age and value I have no idea of, is copper plated aluminum, presumably an attempt to hide the shame of making your money from such a cheap metal. But the lightness gives it away.
Reader Ryan Rotmark sent the following helpful update:
I believe the date on the obverse says "Showa year 14", which is the 14th year of the reign of Emperor Showa, or 1939 on the Gregorian calendar. The reverse says "10 sen". A sen is 1/100 of a yen, so its value is 1/10 of a yen.

I decided to ask Nobuo Takahashi, the Japanese distributor of my Posters, about it, and he replied
The coin in question is called "aluminum bronze 10 sen coin" and
as your reader says it was minted in "showa 14" year.
The value of it in auction varies from 50 yen to 100 yen which
translates to 50 cents to a dollar.
http://homepage3.nifty.com/redpepper/round/10sen_arumiseidou.htm
According to this page, it is made of 95% copper and 5% of aluminum.
The coin used to be made of nickel but due to the lack of metal because of
war between Japan and China in 1938 they decide to make it with bronze.
Bronze usually made of copper and tin but even tin was scarce in that
time the aluminum was used.
So it seems like not copper plated but is alloy of copper and aluminum.
Nobuo
Hm, it really feels very, very light to me.
Source: Japan
Contributor: Theodore Gray
Acquired: 20 November, 2007
Text Updated: 29 January, 2009
Price: $1
Size: 0.5"
Purity: >90%
Sample Group: Coins
Aluminum