JA115651. Brass 4 mon, New Kanei; Meiwa-sen (brassy alloy); Hartill EJC 4.252, JNDA 133.75, Ogawa 329, Jacobs-Vermeule K602, Jones Kanei 200-10, VF, spots of green deposits, scratches, 4.997g, 28.5mm, 0^o, Musashi Province, Edo, Sendashinden Fukagawa mint, kan ei tsu ho, regular characters; reverse 11 waves

 

The very first four mon coins, issued in 1768, had 21 waves on the reverse. Later four mon coins, all with 11 waves on the reverse, can be dated by the type and color of the metal. Meiwa-sen, brassy alloy (68% copper, 24% zinc, and 8% tin), was used for the first 11 wave issue, 1769 - 1788. Bunsei-sen, reddish alloy (75% copper, 15% zinc, and 10% lead), was used for the second issue, 1821 - 1825. Ansei-sen, dark alloy (65% copper, 15% zinc, and 20% lead), was used for the third issue, 1857 - 1859. After 1866, all four mon coins were cast in iron.