Notice the pinhole is threaded, probably to accomodate a small lag screw. Small porcelain insulators from Europe were commonly made in this manner. Most notably you will find this feature on small porcelain knob insulators, but I've seen it on numerous other examples including electrical fence and attic applications.

First email gets this rare Gray Green (1 of 3 known) porcelain no-tie insulators for only $50 plus 6 shipping. Thanks