9Three, it is a bead, (see photo below) slightly small for aging eyes I have been told, but it works for me. All the metal and wood work was done by Gerrie Coetzee in Bloemfontein. The rear sight on the .450 is a wide V, single, robust (and solid) "blade".
I was lucky with the wood, some of it was traded/ swapped very cheap. Like the piece that ended up on the 9.3 I swapped for a sound moderator that cost me less than US$60!
Steve, yes, the .243 works well on baboons, but I mostly use it to cull springbok. (and the occational bigger animal like oryx.)