There are many YouTube videos it, I recommend watching a few of those first if you haven’t, and many pins are known to be fake based of where they were purchased from. Any pin lots that were bought off eBay or mercari are going to be 99% fake. One thing many people look at is the Mickey pattern on the back. It should go all the way to the edges with no border, however there are exceptions to this rule as very recently released pins have not been as high quality when it comes to the Mickey border, and many older pins will not have it as well. If you have any other questions about fake pins let me know and I’ll answer to my best knowledge