This shows that there is heavy damage on this piece, and there's plenty of evidence of it being a dug piece. Sick glass and mineralized fracture lines throughout the piece. Could well have even seen a brush-fire at some point in its life, on account of how cracked it is.

The consensus among a few well-regarded collectors who have emailed me over the past few days shows that this is most likely a Brookfield product. Brookfield made a lot of thick-skirted insulators as well as many more normal-skirted ones as well.