Hello again all, If possible I'd like some advice on how I might tackle this.

Click image for larger version.  Name: oxide.jpg  Views: 20  Size: 40.8 KB  ID: 13158

The above is my attempt at using an ancient copper coin in a piece of jewellery.
While going about things as I normally would, (Soldering, Pickling etc) I caused damage to the original patina.

I had read that putting anything copper into your pickling solution was a bad idea, so I tried to make a string mount to submerge it, (Copper coin to the top, untouched ideally) but I then promptly dropped the whole thing into the pickling solution.
That was an obvious error. I think that lead to the blueish oxidisation you can see,.

But I also found that even soldering around it really changed the surface patina of the coin, and I'm not sure how I would avoid that.

So, the question I have is this:
Is there anything I can do to fully protect the coin while working around it. Is there anything I could cover it with that won't effect the surface?
Any advice would be greatly appreciated!