Do you have a really good digital camera? If so, I'd be inclined to email him some very large pics showing the card at various angles to a strong light.
I don't think it's buyer's remorse exactly, but some people are very persnickety when it comes to cards, and some of those people live overseas.
A bigger problem in my mind is that this tends to be the sort of person who will gasp in horror when they have to pay customs fees. So, while giving a very detailed description and very large pics, I would also state firmly up front that the item will be declared as merchandise and that the buyer is responsible for any customs fees which may arise.
COMC auto accept is currently set at 35% off.