Japanese coins can be dated either in Japanese numerals or Arabic numerals. If they’re dated with Arabic numerals, the Christian date is generally used, so the date doesn’t need to be deciphered. In most cases, however, Japanese coins use the nengo dating system, which I will describe and explain in this short guide.
Nengo dating is the practice of displaying the name of the current emperor and year of that emperor’s reign. For instance, if your coin shows the Japanese characters for Shōwa and 35, your coin was minted in the 35th year of the reign of emperor Shōwa (Hirohito), which would date your coin to 1960.
Japanese numerals (fig. 1, below):
In order to date coins that use the nengo dating system, you must first be able to translate the numbers. Here’s how:
If there is only one number, simply translate that number.
五 – 5
If a small number from Chart A is front a larger number from Chart B, you multiply the smaller number by the larger number.
五十 – 50 (五 is the numeral for 5 and 十 is the numeral for 10)
If there is yet another number following this, the third number is added.
五十三 – 53
Prior to 1948, Japanese numerals were written in the traditional right to left manner on coins. In order to determine if they use that method or the Western method (left to right), simply look for the Japanese symbol nen, meaning year (fig. 3). Nen always follows the date, so by using that you can determine which way the date is written.
NOTE: For the first year of the reign of an emperor, the Japanese character gan is used in place of the numeral for 1.
The second step to dating your Japanese coins is to determine which emperor the coin was minted under. To do this, I have provided a chart (fig. 2) of each emperor from the beginning of the 19th century to the present day. The characters for the name of the emperor’s reign can appear in either orientation as shown in the chart.
The easiest way to determine what date your coin is in Gregorian years, simply take the first year of the emperor’s reign, subtract 1 year and add the number on the coin.
If the date is Shōwa 35, start with the first year of Hirohito’s reign (1926), subtract 1 and add 35. You will end up with the Christian year of 1960.