JAPAN: Keian, 1648–1652, AE mon (4.75g), VF, ex Adam Yeung Collection. This type is recorded in Taisho 7 (1918) without illustration in Toyo zenika nenpyo on page 6 where the author says it's from the Keian Era, but a likely "forgery, yet to encounter a real one." It is also published in Heisei 7 (1995) in Fukunishi izumi izumi fu, Volume 1, and in the Twentieth Issue of Journal of East Asian Numismatics (JEAN), published on Oct 30, 2020, page 74, without commentary. An amuletic example was published by Munro (1863-1942) in Coins of Japan with reverse symbols and characters. Much speculation has been written about why and when this type was issued, still an interesting type.
Estimate: USD 100 - 150