Just got this badboy in the mail and it's not the first CD 131 I've had, but I just cannot help but notice the striking almost duplicate shape these have to the CD 731 threadless. It is my guess that the 731 mould was retooled and reused for these early threaded Brookies. This one also has a huge comet of bubbly spit going completely around the insulator just above the wiregroove lip starting behind St and the tail ending behind 45.