The backside of both haversacks are of leather which runs up and folds over to make the front flap. The tan haversack has a pillow ticking inner liner. The front linen piece is hemmed over and captures the ticking. The stitch is of waxed thread run with two needles in and out. This stitch passes through the leather, the two panels of ticking and the two panels of the linen (front face and the hem), if all that makes sense. This is true on both sides of the haversack. When you pull that all together, it is very strong. It's not going to pull apart, trust me. There are many ways to make a haversack. This is just one style variant. Whether or not it can be documented historically, I don't know.