The interesting thing about this insulator is that something has been hammered out on it.
Albeit damaged, the green swirls are quite nice.
Looks like the shop number was X 2. Perhaps for 2X production?
Yup, it's a blotted A. T. & T. Co. as Jim said. Pretty common, but the neat thing about Brookfield production (and many other insulators) is that you could find lots of interesting variations and production anomalies like swirls, junk, folds even in the stuff that's not very expensive.