This horn appears to be a standard "carry" type horn to me, based on style and size, with the expected Eastern style, dual strap-retention rings on the spout. At some point, it was dropped or damaged on the plug end. The views of the uneven edges around its "bell" or mouth, as well as the uneven lobes, show that it has been shortened during its period of use and reworked. I think the original flat, soft wood Eastern plug was re-used, based on its patina and proper style, and probably reduced slightly in diameter to match the smaller bell from the horn's slight shortening. The period repair used an ingenious method to keep the reworked plug in the horn, with the "new" small lobes with holes for short retaining pins or perhaps iron wires.
Since the horn has strap-retaining rings on the spout, I'd make an educated guess that the repair somehow had a small metal wire loop or other device for strap attachment on the plug end, somehow held by, or a part of, the pins or iron wires that went through the holes in either lobe, and the plug was not opened/closed to fill the horn with powder... such action would have ruined its ability to remain tight and well-sealed to protect the powder inside.
Shelby Gallien