The holes in the coins/硬貨の穴
During tours, I get interesting questions from tourists visiting Japan. Here are the answers to the questions that I got stumped by!
Q: Why do some Japanese coins have holes in them?
(Five-yen coins and fifty-yen coins have holes.)
At first neither had holes. They were created in order to avoid confusion between the two coins and others.
The 5-yen coins were minted for the first time in 1948, the same year as the 1-yen coins. They looked similar, which gave the visually-impaired a hard time distinguishing them. The following year, the 5-yen coins started to be made with holes in them.
In 1955, it was time for the 50-yen coins to make their debut. However, they looked similar to the 100-yen coins, which came into circulation 2 years later. So the 50-yen coins got their holes in 1959 for the aforementioned reason.
There are two other benefits to the holes. One is that they reduce the costs of materials used to produce the coins－about 5% per 5-yen coin and 4% per 50-yen coin. The other benefit is that the holes render counterfeiting difficult.
As a side note, it was not the first time holed coins were created in Japan. From 1636 to 1862 during the Edo period, coins called kanéi Tsūhō (寛永通宝) were produced. Kanéi comes from the name of the imperial era when they started to be cast. Tsūhō means currency. Those four Chinese characters were inscribed on one side of the coin.
Thanks to the holes in Kanéi Tsūhō, it was easy for people to keep the coins together by threading string through them.
The holes in Kanéi Tsūhō coins (made out of copper) are not round, but square. Why is that?
After the copper was molded and cooled down, the rough edge ,or burr, as it is known, had to be filed away. This is why the coins had the square holes. Hundreds of coins were put through a long square stick and their edges were filed down. If the holes and the stick had been round, the coins would have turned around as they were being filed, right? I find it quite clever.