Are these made by Thomas? The bottom right insulator is the same as the one pictured in the top right (and bottom right) of this picture here [id=464882000]. This is a continuation of the question posed on that picture.
There are some slight differences amongst these -- there's one that's noticeably taller (bottom left), and there are some WG profile differences on the two to the right of that one -- but they all appear to be wet process, fully glazed pinholes, similar top of the pinhole and base of threads. The 2nd from the right on the bottom might even be Brent's "chili and cheese" color.