http://www.brownells.com/shotgun-par...-prod9651.aspx
Don't worry about the thread size. I used a pin vise to hold the head then took a Dremel tool to cut the shank down to just larger than the Parker hole. Took the sight held with a pin vise and screwed it into the hole creating its own threads. Took it out and put very minute amount of super glue on it and threaded it back in. Warning: do not use the pin vise to screw all the way in or you will make a circle imprint on the wavy rib if not very careful (don't ask how I know). Back the pin vise to where you can just hold the sight and not touch the rib. Tea or coffee to discolor it. If you think the bead itself is too big (it is rather large, chuck it up in a drill press with a fine emery board to shape it down smaller. Better buy two when you order them.
National Geographic had an interesting article on the mammoth ivory being hunted in the melting snow pack, and how valuable it was to the native Siberian people (and in Alaska as well).
http://ngm.nationalgeographic.com/20...ks/larmer-text
http://usatoday30.usatoday.com/tech/...trinkets_x.htm