When the New Currency Act was promulgated in June 1871, the weight of 1 sen (monme) was set at 3.756574 grams at first, and then in October of the same year, it was reset at 3.756521 grams, so the weight of 1 ryo became 37.56521 grams.
明治4年（1871年）5月、新貨条例公布の際、当初1戔（匁）＝3.756574グラムとされたが、同年9月に訂正され1戔＝3.756521グラムと定められたため、1両＝37.56521グラムとなる。