The BIGGEST problem is the lack of access to original accessories to compare them too.
Your best bet to to find someone who has an original and is wiling to perform basic tests starting with personal photos back and forth. (People who have the originals do not like the pics to get into public domain so that re-casters can perfect the product).
Weigh it and compare.
Float test in water helps sometimes too.
47/50 times I can tell when I have something in hand and am comparing.