To me they look like they have abrasive surfaces on the outside radius of the shoe (worn out) and can be bolted in place over some kind of slot or holder?
a Search of the US Patent office for Weaver late 1800's shows several patents for rock drills chucks and teeth as well as clamping mechanisms for rope and cables. Because you are only finding this kind and an opposing would be required for a clamp, I am buying into tooth bits for a Rock drill. It would make perfect sense to where you found them.
Anyone?