Being the crazy old guy that will pay good money for old rusty gun parts, sometimes has its advantages. A couple of years ago a young man brought a small bag full of muzzleloader parts to my door, and asked if I wanted to buy them. I asked how much, he gave me a number, and I gave him the money.
They were Southern mountain style parts, that the young mans father had rescued from a house fire. The crown jewel of the lot was a nicely formed buttplate. I examined the plate carefully, and could find not find any sign of a rivet. I took it to a friend, that is a metal fabricator, and amateur blacksmith, and he too said, he couldn't see any sign of a rivet. So, we elected to dress off, with a file, the juncture of the "assumed" two piece buttplate, to try to discover how the two pieces were held together. We found that the plate was actually of one piece construction. A waist was filed into the one piece plate, and then the plate was bent to shape over a metal form. The corners were then forge brazed together.
Hungry Horse