Hi,
This is one that is certainly unusual. I might do some research and come back to this. My initial reaction is more with Jonathan's dating, as I first saw very early 1950's. Clues for me are the the wool jersey, and the general shaping of it is different than the 60's space age helmets. It does look to be styled after a driving cap, but worn for evening as it is quite dressy in feel. I have come across Mr. Milton hats and they were, from my experience, all from the early to mid 1950s. The labels look circa very early 50s also. It could be late 40's, very sporty and European in influence. Cool hat!