These are a nice twist(forgive the pun) on drinking horns. We've never seen them anywhere else but doubtless our supplier is selling them to someone else. They're a standard horn with a heavy sidewall that has had spiral grooves ground into it. They come in a variety of patterns but this is the present one.
I wouldn't fancy the job of grinding those spirals. Forget the concentration needed to get the spiral even around the horn, the smell must be horrendous. I've played with bone and that smells when you work it, grinding that much off must be overpowering. Luckily there's no trace of that by the time they get to us.