I used to have a Burns Bison years ago interesting to note about the pickups with Burns guitars you dont see them round much, i have an old set of singles from a Squier too probably similar era, and yes they have the rectangular magnet bar glued on unlike the one in your image Simon, however they are quite rusty but actually sounded quite good thats why i kept them, i may use one in the tele im building just to see what it sounds like.
Maybe the rust and ageing makes them better?