Juen-koka (10-yen coin) (十円硬貨)

Juen-koka (10-yen coin) is a subsidiary coin issued by the Japanese government.
It is also referred to as 'Juen-dama.'
The obverse and reverse sides of the coin are often confused; the side on which the Hoo-do Hall of Byodoin Temple appears is the obverse side.

Summary

On the obverse side appear the characters for 'Nihonkoku 日本国,' 'Juen 十円,' and Byodoin Temple, and on the reverse side appears the number '10,' the year of manufacture and stylized evergreen leaves.

Although it was issued in 1953 (28th year of the Showa period), it was manufactured from 1951 (26th year of the Showa period), therefore the earliest year incused on a 10-yen coin is '26th year of the Showa period.'

Giza-ju (Jaggy 10-yen)

As 10-yen coins produced between 1951 and 1958 have an engrailed rim, they are nicknamed 'Giza-ju' (jaggy 10-yen).

Ten-yen Bronze Coins as Metal

Ten-yen coins are made of bronze, and as such, when immersed in Worcestershire sauce, vinegar, soy sauce, lemon juice, or even detergent, the metal oxide and dirt on the surface is eluted or dissolved, and the coins look shiny as though they had never been used. Making old 10-yen coins shiny in this way is also a favorite pastime among children. However, this also erodes and deteriorates the coins themselves, as it encourages the process of oxidation, develops verdigris, and reduces the coin's mass. In terms of the value of the 10-yen coins from a collectors point of view, such treatment of these coins should be avoided at all costs.

It is said that putting 10-yen coins in a puddle of water discourages the development of mosquito larva. An experiment carried out by the Japan Copper Center in 2006 proved the pesticidal effect of copper ion, and according to the experiment, new coins are more effective.

In addition, one should note that the act of eroding coins including 10-yen coins is punishable by law due to the Act for the Regulation of Damaging, etc. of Subsidiary Coins. For example, the pesticidal effect described above is caused by the elution of copper ion from the coin, which of course causes the erosion of 10-yen coins.

History

1871: The old 10-yen coins (standard coins) were issued.

1897: The new 10-yen coins (standard coins) were issued.

1950: Although there was a plan to issue nickel silver 10-yen coins, it was abandoned as the price of the material soared due to the Korean War, and the coins were disposed of, except those preserved for the purpose of documentation.

1953: 10-yen coins were issued (the coins were manufactured from 1951). These were the so called ''aggy 10-yen' with the engrailed rim.

1959: 10-yen coins were altered so as to have smooth rims, instead of engrailed ones.