Hawk medallion I sculpted a while back, now serving as a testbed for the corroded copper shader I made in week 1 of my shader tests (since I can't distribute it with the Happy Buddha model.)
The tri-layer glossy shader this material is built on is great for a wide variety of materials; I used the same base to make the gold, pewter, and bronze shaders.
Awesome shader, thanks! I used it on my dinosaur sculpt... https://www.artstation.com/artwork/eV4qZ
I tried this in 2.9. I can't Append the material to another file. Indeed, adding a new object in the current file and attaching the same material leads to just the green copper.
Amazing shader. Congratulations!