Although this post is slightly aside,
it is possible that chang's coin is not a forgery or a mule.
I have seen a square Straits Settlements 1/3 Cent, dated 1816, with an obverse image of Victoria,
and also a
round Straits Settlements 3/4 Cent, dated 1820, with an obverse image of Victoria,
both of which seem be be very obviously privately made fantasy coins.
Chang's coin needs further investigation; it may? have the same source of manufacture