The occipital bone (base of skull) is shattered on the left side, on that skull in my first post. This is not evident in the pictures, and the damage is in fact not even visible from the front or side.
I met a buffalo rancher a few years ago and had an interesting conversation with him. He did his own slaughtering, and would run the animals into a chute of some sort, one at a time. He said he would stand on a rail, lean over the top, and shoot the animal in the base of the skull with a .44 Magnum revolver. The buffalo would drop in his tracks. Based on the damage to Old Bull's skull, I suspect he was killed in pretty much the same way. I also bought a second bison skull in 2006, from a shop in Custer, South Dakota, when I was up there on a trip. This was from a younger and somewhat smaller bull, but it was a really nice specimen. I ended up giving it to my son, who is just as crazy about this sort of thing as I am. This second skull has a very neat dime-sized hole in the occipital bone. It isn't visible from the front or side.
I spent my career working in rehab, much of the time with stroke and trauma patients. From this, I gained a little understanding of neuroanatomy. It would seem to me that a large-caliber bullet to the base of the skull would blow out the brainstem and likely the cerebellum. This would probably paralyze the animal instantaneously. If the bullet continues on through the midbrain and into the cerebrum, the animal would also very likely be rendered immediately unconscious. A shot or blow to the forehead might very well make the animal unconscious but not necessarily, and would probably not paralyze it, either. It would seem to me that the base-of-skull shot would be quicker and more humane. However, this is all speculation on my part.
I have seen bison skulls offered for sale and described as having "a dime-sized hole at the base of the skull." However, it does seem now that most of the skulls you see for sale have an obvious hole in the forehead, either from a bullet or the pneumatic piston device mentioned by Appalachian hunter. Sometimes these holes are patched. A hole in the forehead would ruin it for me.
I think there are a very few buffalo ranchers, mainly native-run operations, I believe, that kill the animals in the field with a rifle. I've heard that shot placement behind the ear can make for a quick kill, but I suspect heart/lung shots may also be used. I can't say for sure.
If you are shopping for a skull, you'll want to decide for yourself what is acceptable in terms of damage. You may pay more for one without a hole in the forehead. If there is a bullet hole in the skull that has been patched, the seller should disclose this. If you're not sure, it would be worthwhile to ask.
Bison and humans have a lot of shared history, and for me, bison skulls have a mystic aura that may be hard to describe. Some of you may feel the same way... Maybe not, which is okay, too. These are animals whose ancestors wandered out of the Pleistocene with our own, and I'm glad they are still with us.
Best regards,
Notchy Bob