Scarface,
I quoted two of your earlier posts as I believe they should be considered together.
Better late than never, I missed your post back in May. I'm referencing Fort Hall trade records so 1820's to 1840's era. I am still researching this subject as I am finding it very interesting. The "Rendezvous" era and what is reenacted seems to be against any sheath with a loop attached to the belt, yet they are using fancy beaded sheaths made out of brain tanned leather. I cannot find any evidence to show the historical accuracy of what is being used today. A knife sheath was a utilitarian tool that would have been simple, but useful and really no different that what was used earlier like the Revolutionary War time period for example.
I can't speak to beaded or quilled sheaths, except to say NA's made them, but I don't know if they fit into the 1820-40's time period. I'm not saying they were not, but it is just I don't know. Such sheaths most likely were not "every day" wear for NA's, but rather for ceremonial or sort of their form of "Sunday go to meeting clothes" to make a poor analogy. The NA sheaths that are documented by most paintings I've seen were parfleche and may have been fairly commonly painted, as they did with other "every day" parfleche cases.
I've noticed that it isn't "period correct" to use a knife sheath that has a loop in the back of the sheath to attach the sheath to the belt. I believe this to be a misconceived notion. Fur trade records state that belts were sold with sheaths attached to the belts. The sheaths would have been generic to fit trade knives of the period.
We know that 18th and very early 19th century trade sheaths made in England for Trade Knives were center seam sheaths with holes in them and either tape or leather thongs used to attach them to belts. Though we haven't been able to document this, originals that have survived don't appear to be made one at a time to fit individual knives, which makes sense. They appear to have been made by leather workers on wooden forms that would fit a large number of the same style of knives. That most likely was "their" version of mass production, the same as we can document they made bayonet sheaths on wooden forms. Other styles of the period knives probably also had such "generic" sheaths made for them on wood forms when the blades were more curved or longer, etc.
We can say the center seam sheaths were the most inexpensive way to make a serviceable knife sheath in that period and especially if they used wood forms, as we think they did. That doesn't mean they could not make a higher grade sheath in that period, but there was no reason to for inexpensive knives when they were trying to keep the manufacturing costs down.
I cant document when the English agents/factors switched from center seam sheaths to what I'll call a folded over sheath, somewhat similar to what NA's were making from parfleche. I suspect they did it because their NA customers preferred their sheaths that way, but I can't document that other then in a very general way that over the years of the fur trade, they did make changes in guns and other things, according to the tastes of their NA customers.
Here is a pic of such a factory made folded over sheath, BUT this one supposedly dates to the third quarter of the 19th century, I.E. 1850-1875. This style WAS made to be "attached to belts," but I don't know if this style goes back to the 1820-40's period.
https://i.pinimg.com/564x/1a/f2/7e/1af27e8bef12169908ee7ddff7411e53.jpg
I do not have documentation on any other style sheath made during the period that had a belt loop sewn on the back, so I can't help you there. The only thing I can say is much earlier belt pouches, like the famous "Lyman Belt pouch" from the FIW period, had two loops/straps sewn on the back to attach the pouch to a belt. So sewn on loops were certainly known much earlier than 1820-40's, but I don't know when/if they were used on knife sheaths. Perhaps someone else can get more specific than I can for that time period.
Gus