After reading the posts about the clone U2 I am a little concerned because I just bought a "Surefire" on ebay for a good price. I haven't received it yet but I'm assuming it will come without a box since it was not advertised as "NIB". How do I tell if it is real or not? It is a weapon-mount model, are those cloned also? (I guess any light can be cloned but how common is it?)...