inside out fix would be the best way to fix for nobody to see or know what happened there. I take a coat needle an thread a piece of thread to it. I slip the threaded coat needle thru the chip or open crack from the outside of the horn. I jiggle the needle down the inside of the horn until it exits thru the pouring tip. I pull a bit of extra thread thru the horn an out the tip. I then tie a cotton ball, or a flax ball lump (for you purest)! to the string an mix up some 5 minute epoxy an juice up the cotton/flax lump nice an juicy/sticky. I then pull the reinforced goo lump by the opposite string back towards the hole an pull as much as I can, into an thru the break making a patch from the inside out. I let that guck lump harden an file the extra hardened lump outside the break even. I then take horn dust of the same color, an with my 5 minute epoxy once again, mix an make a horn dust filled thick paste, which is smeared into the remaining break depression making a perfectly even rough looking, horn matching, max strength ,invisible patch............If you wanted to be creative a small bit of stain rubbed over the local area makes it look like it was always there..............This stuff works for me!!!......try it on a scrap piece if you need to convince yourself...................sonny