How To Tell Is A PCGS Slabbed Coin From A Chinese Seller Is Fake?

A fraudster is probably not going to physically doctor a coin to appear like the certified coin. They will just lift pictures from a prior listing. Way less effort.

They're generally not going to be attempting to replicate the appearance of the coin within the slab - that would be a rather difficult trick to get it right, and getting it "almost right" would be worse than not attempting it at all, given the human eye's ability to spot such discrepancies. As noted by others above, a fraudster is much more likely to use a photo of the genuine slab, then ship you a fake slab.

Two things you might try to do in such a circumstance:
- Check the image for evidence of a watermark or removed watermark.
- Do a Google image search for that image.

This will of course only mean that the image was stolen. It's entirely possible for a counterfeiter to actually own a slabbed coin (which they have use as a model for their fakes), take a picture of the genuine slabbed coin themselves, and then ship you a fake.

But if its paid by paypal why would it be a risk? isn't it a money back guarantee if the received product is a fake?

On the flip side, if you send a genuine coin and the buyer says its fake and files a complaint, and then sends you back a fake one, how can you get your real coin back? Are there protections with ebay?

What worries me is that the seller has a 100% feedback, which means they should be dependable, but they just cancelled my order after I won, I guess because I got too good a deal.