Gold is often a tricky sell online unless it is assayed or serialized like how PAMP ships. It is much more cost effective to counterfeit gold then it is to counterfeit silver (not implying yours are fakes). Right now my local coin shop is selling 1 oz rounds for about 1 bitcoin over your asking price and in my opinion I would rather buy local from a known source at that price difference. Just my two pennies worth.
I have found that after handling gold for even a short time that fakes are very obvious, I have most of the coins this guy is showing and I can tell you that the color and definition is all right. Just from the photo I can tell those are the real deal.
The fakes generally are not very good, they lack definition and are not even close to heavy enough. Silver is more often faked with success than gold is.
I agree with buying locally, but selling locally sucks around here. The only folks around want to give me 60%, ya right.
As metal prices go up fakes get more and more advanced. If the coin was filled it would have the exact same luster and not be worth nearly as much. Even 1oz silver rounds are starting to be faked now.