Thanks a lot for the historical summary!

The Kodalite IV does have the screw and post terminal, and I tried to mount it on another Hawkeye in the guy's store and it fits. Now more questions:

Can Midget and Bayonet bulbs fit in the same flash unit, or I am limited to one?
Is the number (3,4,5) just related to the power of the flash or does it affects the socket size as well?