Shane -
The heads in the auction look like 1939 sloped shoulder blades with the 1942 ferrule.
Did not show the heads in the auction in the 3rd Edition, but have had several of them for many years.
Zwickey made lots of combinations of parts over the years. When you understand the Zwickey manufacturing process, used for the last three quarters of a century, it becomes obvious why so many combinations of blades and ferrules are in existence.
The narrow blade and the convex cutting edge are noticeably different that 1942 Bear Special Order Zwickey with its much wider blade and distinctly sloped shoulders.