Sorry about the ordeal, FR. I spotted the coin on ACSearch...yep, a major auction house.
I am reminded of page three of the "Too Much Yellow!" thread that developed yesterday - specifically Palouche's two coins. The fundamental difference there is that the dealers we are dubbing "A" and "Z" very obviously do the bogus patination work themselves and, in the process, create a very distinctive - easily attributable (as their own handiwork, one orange, one yellow) - look. I thus knew immediately which two dealers - of the hundreds of them in the world today - each of Paul's coins was purchased from.
With your coin I am not so certain that the fraudulent work was committed by the dealer himself (or in collaboration with folks at the neighborhood polytechnical institute either). I think we'd need more evidence of a longstanding tradition, as with "A" and "Z," who I've been tracking for years. The work on your coin may well have preceded their acquisition and simply gotten by their vetting system. This could be a case of a dealer who should know better, being overly lax in the vetting of their inventory. If there are other similarly patina'ed coins in their current inventory, this may be a situation where a large lot was purchased from a disreputable source. Just speculation, of course. But, of course, the dealer is responsible for what they stock.
Glad you finally heard back and that they expressed remorse, and that you're being refunded. Sorry you had to deal with this. Stressful!