Civil War/Indian War Corpsman Canteen

Description

This one's a mystery It's an oversized hammered copper canteen with a heavy leather strap.
I have shown this to a few experts who have not seen one like it.They agreed that it was too big (12 inches in diameter) to have been carried by a soldier in the field and would have been carried in a wagon or horse. I found one that was close by googling large Civil War canteen. It  was very similar  and was from a  1980s sales listing from a New England CW dealer.It was actually an inch smaller in diameter than this one.But that one was described as a Confederate Corpsman canteen that was used to tend to the wounded. I posted photos on Civil War Canteens (fb group) and got opinions that it was a wagon or horse canteen possibly used by a corpsman.No one seems to have seen another example.The sling straps are not soldered as you would see on a typical CW soldiers canteen,but I beleive that might be because the pins offered more security because of the additional size and weight.  Another interesting thing is that it's 2 inches wide at the spout and transitions to 4 inches at the base. The original cork stopper has fallen into the canteen itself. So  to sum it up. not sure if it Civil War or post war..and a few were of the opinion that it was a corpsman (medic) canteen.It's a beautiful piece in any case. If someone can positively identify it,please message me and I will update the description.
Thanks