Very cool find JP..
Was the copper bolt placed into the drilled hole with the brass wedge friction fit in the slot of the copper bolt, and then driven down till it bottomed and splayed?
I think the brass wedge in the diagram was a separate monument used for cracks in rock formations. There is a description for a "brass wedge" on one of the peaks near Spearfish that was used as an early triagulation station, but time ran out since it would have been a half day hike to get to it. Next time!
I think you have it Gordon. Wonder how long it took with a star drill to make the hole.
jud
Same thing from the Adirondack Mountains of NY
and then a slightly different, earlier example from 1873 as set by V. Colvin on the third highest peak in NY (Mt. Skylight) Note the cut in the bottom stem
which would expand over the STEEL wedge shown here
Jim Vianna