That finish is simply a spray lacquer on pot metal. It will wear off
The Oppi Utrecht book should have the patinas you want.
Tim and I just finished re doing our kitchen. We made our own copper
counter tops, hand forged copper pot rack, electrical plate
covers, refrigerator handles, and all hand forged copper drawer and
cabinet handles. When I went shopping for the handles I brought some
home and messed with them to see if I could get a plain copper or
brass finish on them. That’s when I discovered that they charge
really big bucks for spray painted pot metal. It would have run us at
least a few hundred dollars for all that we needed.
I was so disgusted that I made ours from copper bar stock.
Have fun and make lots of jewelry.