Elnathan said:
No evidence that I am aware of for patch knives per se, but there are a handful of original pouches that have one (or two, as in one example) knife sheaths attached. So, if you want to include a sheath on the pouch go ahead, just be sure to think about what could happen if you slip and fall on it and build you sheath accordingly.
Two very good points.
1. Some 19th century pouches had one or two knives attached to the strap or body of the pouch, as you mentioned. The knives look like they are small general purpose knives that could well have been used for cutting patches, but also for anything else the hunter wanted to use them for.
2. Special care should be given when attaching the knives to the strap or body of the pouch. The few times I have done it for others, I made darn sure I included a thick welt of leather all along the length of the cutting edge and the point, to ensure the knife could not cut/stab through the leather in case one slipped/fell with the knife on the pouch.
Many years ago I ordered a 4" knife blank from Indian Ridge Traders to make a patch knife. Though already heat treated, the blade was THIN at around 5/64", of uniform thickness and square on the end. I decided to hollow grind it on one side only, as the blade was so thin and just rounded the tip of the blade from the back down to the edge, as in a sheep's foot design as shown in the following link to ensure it could not stab through the sheath with thick welt I added to the pouch strap. I used curly maple for the slabs for the grip.
https://knife-depot.com/pages/sheepsfoot-blades
In use, I put the flat/unground side on the barrel muzzle so as not to damage the muzzle. Because that blade was so thin to begin with before hollow grinding one side, after hollow grinding one side it could be easily sharpened "scary" sharp even though I only sharpened the ground side and not the flat side (just took the wire edge off that side). It cut thick patches like a dream. A good friend liked it so much, I gave it to him. Unfortunately, those blades are no longer available.
I never found historic documentation for such a thin knife blade that was hollow ground on one side only, though. However, Sheep's Foot or Blunt Tips on knives were common for sailors going back into and before the 18th century.
Gus