Now for Japan. This would be called "Katou Eiraku", meaning a copy from a Yung-lo retooled for use as a mother cash. The coin is non-magnetic, 24.2mm.
The retooling is to deepen and sharpen edges so the newly cast coin doesn't lose sharpness. Yung-lo have shallow relief to begin with.
Here the cutting accidentally went into both the rim and the centerframe. No regular issue of Yung-lo will have that. Then there are a few other very minute evidences of tooling. These coins (assuming this is Japanese) were made as an outlet for copper production. That is, to sell copper, not to counterfeit underweight coins or adulterate alloy. In Japan there were used some wholly new-carved mother cash for Yung-lo, which are scarce to rare, and I don't have any.
Katou-sen overall are any of the many recut copies of all kinds, but most often Sung, made in Japan after copper was discovered and being smelted but before there was a national coinage. Unlike the Yung-lo copies, they got really creative with changing the Sung cash.
This piece being non-magnetic makes it kind of an orphan, which came in a lot of 12 which could not be sold as genuine Yung-lo nor the somewhat valuable definitely Japanese pieces. So for $10 came the 8 previously discussed Vietnamese copies, 2 katou-eiraku, one shima-sen, and one worn original.
