rotative cup on the front of the bars?

[pella]

Do someone know the purpose of that? The saddle tree of my old Textan western saddle have a kind of rotative cup on the front of the bars...strange, i suppose it is to adapt to degree of shoulder? The thing i dislike is that it is a little too round, look like it dig into the shoulder.

The tree is wood covered with rawhide laced with nylon. If i change the shearling on that saddle i'll take pictures. I dont know the age of the saddle, but there is a code, if someone know how to read it...it begin by 79, maybe thats the manufacturing year?