The history of gold minted coins in Japan, and in particular the Japan Gold Yen coin is traceable to the introduction of the yen in 1870 during the Meiji regime. The rationale was to bring about a simpler currency system than the mon-based one that was used during the Edo period.
The Japan Gold Yen coin was introduced through the 1871 New Currency Act with a legal definition of 1.5g pure gold. The denominations of the gold yen included the 2- yen, 5-yen, 10-yen and 20-yen coins that were introduced in 1870 while the gold 1 yen came in in 1871. The original sizes of the gold yen were halved in 1897. Japan would later move from gold standard systems towards the end of 1931.
The gold 2-yen coin lasted between 1870 and 1892 although the official demonetization was in 1992. With a smooth edge and a circular shape, it has a gold content of 90 percent while copper accounts for the remaining 10 percent of the alloy. The 2-yen coin weighs 3.33 grams with a diameter of 17.48 millimeters and 0.096 t/oz gold. The circular 5-yen one is 21.82 millimeters wide and has a hole at the center with a diameter of 5 millimeters. It was issued first in 1959, has a mass of 3.75 grams and an actual gold weight of 0.2411 at 0.9000 fineness. The circular 20-gold yen coin was minted between 1870 and 1932 weighs 16.6 grams and is 35.06 millimeters wide. It is a gold-copper alloy whose actual gold weight is 0.4822 (90% fineness).
The 2-yen and 5-yen gold coins have similar features. Their obverses have 2 beaded circles, several legends, and a coiled dragon in the middle. The reverses contain the sunburst crest on a sacred mirror, military banners, paulownia crest to the bottom and chrysanthemum to the top. The 20-yen coin has a date at the bottom, cherry blossoms separating 3 legends and a sunburst mirror. The reverse contains denomination and value inside a wreath while the chrysanthemum appears on top. The Japan Mint, which was established in 1871 in Osaka, is the official mint. Trading in Japanese bullion coins attracts 5% tax.