Thank you, poconopen, for the good comparison photo. It also shows the sharp details of a genuine one vs my soft-looking coin. I know it came out of China in 1958, ruling out a forgery by recent techniques. My guess: an altered original coin, this was then cast from it. What might be the motivation - to create a numismatic rarity for collectors of the 1940s-50s in China, or might a forger of circulating coins around 1923 have thought to escape "the letter" of the law by creating a piece that never existed, thus not technically a forgery? I have heard of this logic among forgers elsewhere.