Not all the Sierra boxes are wrapped that way (as it is said at Vintage Sierra). They weren’t in the first years (see this feature http://www.game-nostalgia.com/sierra/sierra_collector_riddles_1.html)
and also the bigger white boxes with sleeves of a later date didn’t have always folded shrink wrap. Some of the boxes come in both ways; I have checked this a few times and they include the same original Sierra contents. Decisive for the early boxes is the tanned/beige inner box and the system requirement stickers. For the bigger white boxes only the stickers may help to identify their origin.