I have seen a couple of modern poor boy rifle at rendezvous, with leather buttplates, both did not wear well, because the leather was not treated at all, and the butt plate was simply nailed on with small headed nails. Long ago, before I know what I was looking at, I got a chance to view, and handle an old Dutch musket that had been shortened, half stocked, and reused as a fowling piece. It had a leather butt plate made of jacked leather, held on with large headed copper nails. I suspect some native owner in the past removed the original butt plate, to make a hide scraper, and another owner replaced it with the leather one. The leather had been boiled in some concoction rendered it nearly as hard as iron, and allowed it to wear quite well.
Hungry Horse