Kaei Isshugin

...Nanryo means high-quality silver, and like the Bunsei Nanryo Nishu silver coins issued in the 7th year of the Bunsei era, it was of high quality, but its weight was reduced to 2.62g, less than half the weight of Nishu silver (7.5g), and it was degraded. The Kaei Ichishu silver coins issued in January 1854 (Kaei 7) were even lighter, weighing 1.87g. At the time, 1 shu of silver was equivalent to 250 mon, and it was used to pay the daily wages of laborers working at the batteries (cannon batteries) that were being constructed on the shores of Shinagawa Bay (now Tokyo Bay) for the purpose of coastal defense, so Ichishu silver coins were also called "Odaiba."...

*Some of the terminology explanations that refer to "Kaei Isshu Gin" are listed below.

Source | Heibonsha World Encyclopedia 2nd Edition | Information

…南鐐というのは良質の銀を意味しており，文政7年発行の文政南鐐二朱銀と同じように上銀であったが，量目は二朱銀の7.5gに対し半量以下の2.62gとなっており改悪されていた。ついで嘉永7年(1854)1月発行の嘉永一朱銀はさらに減量して1.87gとなった。当時，銀1朱は銭250文に相当しており，品川湾(現，東京湾)岸において沿岸防備の目的で築造中の台場(砲台)の人夫の日当の支払いに用いられていたので，一朱銀は〈お台場〉とも呼ばれた。…

※「嘉永一朱銀」について言及している用語解説の一部を掲載しています。

出典｜株式会社平凡社世界大百科事典 第２版について | 情報