Alnico Blue in one of Treys Deluxe Reverbs...

[cactuskeeb]

You can fairly well match it, point by point, to the current alnico speaker tone tubby.  It HAS to be that speaker frame, and the fact that it's blue suggests it is a special request - perhaps from the old, pre-hemp cone era of Tone Tubby, but late enough in the game to get the frame that would become the generic model for the hemps.