Well, I might as well chime in here also. I believe you guy's are pretty well correct in all of your observations. I kinda took a survey by going through Mr Madison Grant's book and from the pouches he has photographed, I agree with you both. The pouches that have the straps secured with some type of round or D type ring were made around the 1850's. Some were sewn on a machine, which pretty well sets the cutoff date of it's manufacture to be mid 19th century.
He does address the use of rivets as being made mostly of lead and not copper. A great number of the pouches have a buckle adjustment, some even having two buckles. When I make a rifle pouch, I set it up for the buckle to be on the front strap, whether it be right or left hand carry. A customer of mine from Kentucky always wants his set up like I would normally make a left hand carry bag, but he carries it on the right hand side. This puts the buckle on the back strap. He further pointed out that a majority of Mr Grant's pouches, that had horns attached, were set up in this manner. I looked in the book and he was right.
Gary, I think you are right about the O and D rings being favored by the British sporting crowd. As far as lining a pouch, I really have never seen any old original with a lining. I have made two that were lined at the request of a customer.
I'm sure there are some acceptions to what we have pointed out and someone will come up with a lined pouch with D rings on the strap, that came from Virginia, dated 1754.
Frank