The point was more to illustrate that boxes were potentially different between packing plants.
They did have UPC codes when the boxes shown were issued. I believe the boxes I scanned were 1979. (The only ones I have scanned)
The UPCs printed on those inner flaps are probably the last 5 and the small number printed outside the barcode to the right. That's the part that indicates the exact product. I can check next time I look at the boxes, which might be quite a while.
Checking Ebay the 75s did have an abbreviated UPC code. Most of the unused full boxes are "King Dons" known under different names regionally - Big wheels or ding dongs. Because of a conflict with a similar Drakes cake.
The ones I see on Ebay have a different set of info from the later boxes I'd scanned.
http://www.ebay.com/itm/1975-HOSTESS...jcsU19k_y2rz-Q
The licensing info is in the copyright notice area, and the lower left hidden flap just next to it has some useful info. A CCA logo, Container corporation of America and a position number probably showing where it was on which sheet.
The boxes that have the almost always creased cards are "Ho Hos"
http://www.ebay.com/itm/1975-Hostess...EAAOSwAuNW8JrE
That one has the same copyright info, and the same Pennsylvania licensing, but the logo on the right end panel indicates a different producer of the packaging. (Not a familiar logo to me)
It would be a massive project but maybe a bit fun to make an attempt at listing as many of those differences as possible.
Steve B