My thinking was, "If you pick up a raw comic, how would you possibly know if it was a Stan Lee file copy?", but your post answers my question, that they were all slabbed before they were sold for the first time. So I assume that means every Stan Lee file copy is in a slab, unless someone cracked it out, which wouldn't be too smart.
Hehe, actually, I'm still not certain whether I'm going to crack that out or not. Its not a pricey book, and I'll still have record of the sale (printed out, pictures of it in the slab even if necessary) and the CGC label to go with it. *I* know its a File Copy!
The only slabs I have until that one shows up in the mail are Spideys, but I have a nice run of OO Furys in an acid free box waiting for that one to be added to it. =)