https://www.invaluable.com/auction-l...adg-C294F7DA12
The C&T photo with both the 2 tone brass and gilding metal variant and the all w/m version.
The 2 tone one is hard to find. I suspect a makers variation possibly made in error or incorrectly due to a shortage of the correct metals.
The all w/m one is interesting and there are a number of possibilities for its wear but I can find no reference or reason for its use.