Here is what Chris did,
Use a paper towel and prepared yellow mustard.
Coat your coin with mustard and let dry 24 hrs,
Use water to rinse and clean off,after 24 hrs, might need a toothbrush to get dried mustard off.
Repeat coating and cleaning for 6 days.
On the 7th day drip water on coin and let dry in the sun.
Clean her up and you should have something close to the 4th picture
Thanks again Chris
You should post pictures of your knife thats a beauty