Sold Coin on Ebay

Greetings

I sold a silver 1997 Queens Beast Coin coin on Ebay, checked the condition to make sure it was to the same standard as I would add to my collection and despatched it. The seller bartered the price down but not worried, and the sale was 'No Returns' (a number of my friends have said coins are often returned but are not the same coin despatched)

The buyer is claiming it is patinated, has a yellow tinge and decolourisation round the edge (black). The coin was stored with the rest of my silver bullion 1oz 2oz and 10oz coins in capsules and then in wooden cases/boxes. I have been checking my remaining coins and I have in excess of 50 coins going back to 1999 and I can find not a single blemish mark or hint of decolourisation on any coin. I purchase my coins from bullion dealers and have done so for many years and usually already capsulated but if not I have a number of capsules I insert the coins into (while wearing gloves).

I had this coin twice in my collection both from the same supplier two months apart (I keep the sales invoices, I know boring)

Any idea on next step?

I'm no expert, but this sounds like a shady buyer trying to strong-arm you into either reducing the price even further or getting you to accept a "return" where they send you a clearly worse coin than you sent them. If you took clear pictures of the item and had an accurate description, you can try reporting the buyer, but it might not accomplish much. Unfortunately, eBay tends to strongly favor buyers which leaves bad actors with a lot of leverage. If you stand by the sale (and it sounds like you did your due diligence), there might be no avoiding negative feedback on this one.

many thanks for the advise, I also believe that to be the case, I have a number of photographs though not all as clear as I would like I think it is the re-assurance as I sold a coin I believe was in a very good condition for a 2017 coin and one I would want in my collection.

Your best case of action is to inform ebay to the fact your suspecting fraud and go from there.