Very familiar with the cap horn. When I bought Earl Cureton's horn business, that was one of the items he/I made.
As was said, it is a small horn, maybe the size of a primer horn or even smaller. I have no idea of the number, but it is safe to say I made and sold dozens and dozens of them. Never kept track of how many, but it was a bunch. Just like other sizes and styles of the Cureton line. Thousands, literally.
John