Ansei Nishu gin silver was Keisu ginka (a silver coin whose value is determined by the amount written on it) minted only for international trade after June 25, 1859, with an intention to prevent the outflow of koban to foreign countries in preparation to the opening of Yokohama Port scheduled for July 1, 1859, due to Japan-U.S. Treaty of Peace and Amity, and it was also called Boeki Nishu (Nishu for international trade).
安政二朱銀（あんせいにしゅぎん）は日米和親条約による安政6年（1859年）6月2日の横浜港の開港に備えて、同年5月25日より小判の海外流出防止の目的で貿易取引専用に鋳造された計数銀貨であり、貿易二朱（ぼうえきにしゅ）とも呼ばれる。