Several of the record companies at the time did not necessarily seal their entire album as a package, they sealed the vinyl record in plastic then left it in an open jacket. You frequently find old records in plastic sleeves with a serration along the straight edge, those were such that were opened and played. This one has the plastic unopened and the record untouched. The jacket has on the back some aging you will notice around an album sized less aged area, it might suggest it was on top of a stack upside down and there was an open 12" vinyl on top protecting that area. I cannot vaguely say if this is what happened but it is what it might look like if something like that did happen.