Mainly on the HY35s HX35s and HX40s you look for the metal tag. Most holsets you find with have an internal wastegate its just that picture doesn't show one.
If you can't tell just post a picture of it in the turbocharger section and we can tell if it is or not.
holset are fairly cheap, so why would anyone buy a fake.. now if a holset was triple the price then it would be different. Ive a had a Evo 16g ebay fake on my truck for 20,000+ miles with no pproblems..