Frank,
Note the answers to your questions below.
Dennis
1. Is there an inside pocket and where is it sewn ?
No pocket at all.
2. Is the flap sewn on or is it a part of the back ?
Actually the top 2 inches of the back of the pouch is a different type of leather, looks like it might be deer skin or something that is tanned completely different from the rest of the bag. Not sure if its a repair or he didn't have enough of the other kind of leather and used this to piece it out. I tend to believe the latter. the ends of the straps are sewn to this added piece. There also is a sewn up slit in it, looks like the side near the front/back seam, just below the strap may have split on him and he whip stitched the split.
3. How wide is the strap ?
Its 7/8" up toward the shoulder and a tad over 1 inch where its attached to the bag. Possibly stretched/shrunk in the thinner areas.
4. It looks like the pouch is sewn wrong side out and turned, is it sewn with a welt or without ?
Sewn as you suggest and no welt.
5. What kind of leather is it made of and about what weight leather is it ?
I believe the bottom/strap is cow leather except for the 2 inch piece mention above. I am not that familiar with the different weights but about the same as the thicker leather pouches used today, except the 2 inch piece mentioned above is much thinner.
6. Is it lined or unlined ?
Un-lined.