This 10 mon piece of Japan is really interesting (thanks for the pic, KM). It reminds me of the first British coins struck with the steam press in Birmingham, the cartwheel penny (KM 618) and toppence (KM 619). They were hailed as a technological breakthrough. Here's a cast Japanese coin (KM 57) made almost 100 years earlier obtaining the same effect of a wide border with incuse characters.
But what's really funny about our Japanese beauty is that I've been told that the four characters on the edge read Ei Kiu Ze Yo, meaning for eternal use. However, the coin was issued in 1708 and withdrawn the same year (thanks, William). Those inscrutable orientals...
Peter