Wikipedia
Ichibuban
The was a monetary unit of Japan. The Ichibuban could be either made of silver or gold, in which case it was a quarter of a Koban.
The gold Ichibuban of 1714 had a weight of 4.5 g, with 85.6% of gold and 14.2% of silver. The silver Ichibuban from 1837 to 1854 ( Tenpō Ichibugin, 天保一分銀, "Old Ichibuban") weighed 8.66 g, with an alloy of 0.21% gold and 98.86% silver.
The Nibuban was worth double the Ichibuban, and half a Koban and was also a rectangular coin.