1970 Kellogg's Football Factory Set

I've bid on a few 1970 Kellogg's factory sealed sets, but I've never gotten close to owning one.  The pictures below are from a set that is now on ebay.  

This is the only Kellogg's factory football set.  I would have a tough time buying one of these for big bucks because I'd have no way of confirming that the set was unopened.  Is there a way to tell if this set has been resealed?

This guy even saved the edges of the sheets.  I like that.