What I meant was a sheet of stock added above and below the cardboard stock to protect it in transit from the paper distributor or mill to ESCO.
I'm not sure how Dexter shipped, But since it's the back only from a coke premium I'm pretty sure it's a protective sheet that just got into the production stack and went all the way through.
The shop I worked for got most of the paper in boxes with sometimes a sheet of kraft paper wrapping it if the stuff was expensive. Other stuff came on pallets stacked about 5 ft high. 2500 Lbs of paper stacked and wrapped with a heavy paper wrapper. But it usually had cardstock top and bottom. And a couple heavy corner bits to protect the whole thing from the straps holding it to the pallet.
Those cardboard sheets were occasionally the exact same stuff Topps cards were made from. I had the guys make me a few gag cards that were blank on both sides.
Steve B