I recently bought this EIV VHT-20T 2-part glass power insulator from "Open-Wire" . Aqua-blue glass, two shells, This version has a flat topped dome, rather than the "crosstop" cable grooves. .Vintage appears to be fairly recent, 1980s or 1990s. I took the liberty of using his supplied photos (as they wouldn't look as good sitting in an inch and a half of NC snow).

The cross-top version (CD 395) can be seen here: [id=263652912]

"VHT" stands for " Verre Haute Tension" which means "High Voltage Glass" in French. This is the smaller sibling of the VHT-22T