I got the horn button off. I used four putty knives and two wood shims. I got the two thinnest blades started on opposite sides - 3 and 9 o'clock. Then I started a wood shim to increase the gap - at 6 and 12 o'clock. I then inserted the next thicker blade until I could put two thinner blades in at the same point. I tapped on the wood shims to increase the gap again. Last step, I put the thicker blade between the two thinner blades and used it like a wedge. POP! it came off - and in ONE piece. The other important tool I forgot to mention was the extra large portion of patience.