You have my symathyies with this, Ive to have found to my cost and
aggravation, that people, rings and surface patinas never rarely
work well together.
Regretfully I have to say beauty always fades with time, even if the
heart stays the same.
There is no long lasting solution. All you can do is offer the
customer his money back on the safe return of the ring.
I guess thats why wedding rings are from solid gold not plated!!.