tosborn

It looks to me like these are local survey marks for a curve - probably for a road or a railroad. PC - "point of curve" is the point where a circular curve begins. PT - "point of tangent" is the point where the curve ends.

I've contacted a friend who lives in Cimarron, NM to search for the monument there. The coordinates given above for Cimarron are 36 30 10.01 lat, -104 54 59.04 long. BuckBrooke....if you search there before he does, here is the presumed location on a topo. The red dot marks the spot just South of the main town: