How can you tell if a juicy couture charm is fake?

I don't think they sell fake one's the real one's come in juicy couture boxes and when you look at what kind of one's there are you will know what the real one's look like. Juicy Couture charms they have like a little stamp which looks like a crown on the jewellery the one the charm is hooked onto. They cost from £40- £60 each there's loads online. There usually the same one's in every shop or internet website.