Japanese Tsunami Nail Knob Mystery

Last week while visiting the Coast I enjoyed meeting a fellow artist in Moclips by the name of Lee Pickett. This gentleman has gathered several interesting beach debris items, mostly wood, that in all probability drifted across the Pacific after the 2011 earthquake and tsunami in Japan.

The bowed timber is Douglas fir, meaning that wood came back home.

The most mysterious object is what appears to be a ceramic unipart nail knob insulator for electrical fences. To help Lee out in learning more about this item, I have approached several collectors concerning the marking on this insulator and so far no one can identify the source. Any of you readers out there know?