Four characters - Kan Ei Tsu Ho / Blank. 23mm, 2.70 grams. Mint in Fukagawa, cast 1739-1741. Hartill 4.173.

Cast for 3 years from the 4th year of Gembun (1739). 

Most Japanese coins are very rare. These coins are, however, common - they were inspired by the Ming dynasty cash from China. "Kan Ei Tsu Ho" means "Universal Treasure of Kan Ei".