Don't cut 'into' the large end. That is called the button or the crown and is valued as it is. You could cut it off the rest of the horn and sell as a seperate piece (keep those little fingers on the crown piece). That rounded end can be polished and some scimshaw that piece and make belt buckles or other jewlery type items.
If you look at the other end, where there appears to be two surfaces, you will notice one (the larger) appears to be 'pithy'. That is the main horn and it will be 'pithy' all the way down to the crown. I think the best part of any antler are the points...not the main beam. The main beam always has the pithy center, much like a bone has marrow, but the points are more solid and ivory like. The pithy part can be bored out and the outer portion will still have the solid ivory that you are looking for, but sometimes the main beam is so thick that by the time you get it turned down to the proper diameter, you are into the pithy part.
That piece might make some good butt caps or joint material on a few cues, but it is too large for ferrules I believe. Still a good find and a good buy for someone to use in the correct place.
Good luck with your sale. I hope this info helps...not trying to spoil your sale.
L8R...Ken