Thank you, bbhf, for the additional pictures and description! It looks almost as if the pouch body was made of two pieces of similar leather, stitched inside out and "turned," and the thin leather facing was stitched to the front panel, effectively making an outside pocket. It looks like the front panel of the main pouch, which serves as a divider, is somewhat larger than the back panelThis explains why I first thought it had a gusset. I suppose the thin leather facing (the "outside pocket") would have probably been stitched to the front panel before the front and back were joined. The flap could have been put on last.
This design looks like a good way to make use of smaller pieces of nice fur or leather, reserving these for the flap and facing.
A hunting pouch is such a simple thing in concept, yet the variety of designs and ingenuity of construction continues to astonish me.
Thanks for showing this fine old pouch and horn, and for taking the time to answer all of our questions!
Notchy Bob