From what I read on aa, 1932ish? Perhaps we have some other brazil examples here on the forum? I find the early sk stuff interesting, as it looks like old sears, hinsdale duro etc...
Just to update, I have looked at an sk set of the same time period and the sockets in that set have the 2 dots as well. In fact I could discern virtually no difference between the sk and the brazil sets, even the boxes are the same...