I finally got around to working on restoring this horn. Think it turned out pretty well.
I cut out a plug from a piece of cherry that I had in the scrap box.
Installed and distressed the plug. There was a small amount of mouse damage on the lip of the horn at the top of the picture so I extended that into the plug.
Had to make some new rusty nails as I could only reuse some of the originals. I also carefully scraped off the little white paint flecks that were all over the horn.