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In China/ HK, there is no such thing as CuSn8. CuSn8 is an brand name of an alloy by a swiss company. A company in Germany sells a similar Copper Alloy but it goes by a different trade name.
They only know of the following types of Brass. Yellow Brass (Pure copper), Green Brass, and Pink Brass. What everyone has been getting thus far is Yellow Brass. When we first asked for Bronze, that was what the case makers were suggesting. That's because Yellow Brass watch cases are already being made nowadays mostly for lowend/ cheap watches which then get plated. Brass is also widely used and easily available in the watch industry.
When I told them NO, I want bronze, and bronze has a pinkish hue, they then told me, easy, just take the brass and plate it with rose gold! That's why some cases you have seen thus far have had a pinkish hue replicating CuSn8 Bronze but does not patina/ tarnish easily. As the pink hue is actually from a plating (which also tarnishes mind you, just not as quickly).
When we tried to locate the material ourselves in China, we managed to find a couple of suppliers for Bronze. However Bronze is generally sold in sheet form. This is not suitable for watch making as it is too thin. In order to cast the required size for watch cases would entail 3.5 tonnes of CuSn8 to be processed. The closest thing you can get is what is called Tin Copper or Phosphorous Copper. However the composition varies, sometimes you may get CuSn6 and is not the same as CuSn8.
The final solution we came up with was to actually 'create' the mixture for CuSn8 with a materials supplier in China. This is done by giving them the material composition and getting them to mix it and cast/ forge it. The purity for sure will not be similar to CuSn8 from switzerland/ germany but it will inevitably have a similar range of metal composition and be a lot cheaper.
Do note that there is no real history in the usage of Bronze for watch cases. It is actually a new material introduced to the dive market, and in reality the material CuSn8 is only popular as it has been shown to be what is used by some of the bigger brands for their Bronze watch offering.
Personally I feel that watch cases should not be constrained by this, that brands should be allowed the freedom to experiment with different alloys for a similar effect. But brands should be honest about what they are giving their customers, case in point Kazimon, not a CuSn8 case but a great selection of Bronze nonetheless. We are doing our version of CuSn8 because we like the colour/ hue, and the patina it gives. Hope that it works out well, it is a huge investment but it suits the look of our divers so we will try. That's the short version of the story by the way, hope you have a better understanding from where I am standing.