I am wondering if the "welt" across the bottom is actually the lower edge of the divider?
The construction is a prefect way to add a full divided panel that you can still fish stuff out from the bottom of...bellowing the bottom even just that little bit causes enough swell at the bottom of the bag so it remains accessable.
I wonder about the strapping...it looks like heavy horse tack or harness type leather...
I also wonder about the extra exposed awl holes on the front panel...was the leather recycled?
That could explain the heavy strapping?
Just my own thoughts and guesses based on what I can see in the photo. That bottom detail is really interesting, well thought out, and well constructed. That is a neat old bag.
tc