[Blunder19]

I am thinking about putting together a collection of all the topps packs from 1951-1975. When collecting sealed packs how do you make sure the pack hasn't been tampered with, if buying raw?

Is there anything I can look for in the scans that may help me to determine if a pack has been opened and resealed? I would really appreciate any help on this subject so I don't get burned while trying to assemble this collection.

Also.. aside from ebay.. does anyone know where is a good place to find sealed packs?

Thanks
Jamie