Kevin,
The Chinese whistles are actually cast iron copies of the Star Brass whistle! I've got one of each and you can clearly see that the Chinese copied the Star. Casting quality is crude and the inlet is the metric equivalent of 1 1/2" but that leaves a lot of extra metal inside the flats, so many people have simply drilled the Chinese whistles out to 2" and tapped them for 2" npt. I've heard some QJ whistles that sound wonderful, others like total crap. I'm sure it depends on the way the particular whistle was machined and set up.
Michael Allen