Same design as Brians exactly - number just pushed to the outside of a flange that faces the shooter. Carbon fiber or other tube mounts or glues to flange.
Just an idea. I know people do just fine as is. It's just I've used a Bushnell with a rearward extension like that for the AO and it's great for ergonomics. Depending on scope position it saves you some critical inches you need to reach forward.
It seems with the clamping that the nylon ring shouldn't slip on the Bushnell AO's metal. You could even put some rubber cement inside the ring or some other contact adhesive that could clean up later. After all people use scope sidewheels and they don't turn independently of the hub they are attached to, right?
EDIT: Found the real life version! Numbers on the rear flange too so even easier to read.