Yep, used as air raid warden helmets, auxiliary police, fire etc.  Some have decals, paint on them for the "branch" of Civil Defense. One of the sleeper collectibles that I think will be gaining in popularity.

It's actually the 'MAY' that would concern me most 🤭    

I have a 1937 FIRST CONTRACT IRVIN FLEECE Flight Jacket that I planning to sell.  I can not remember the pilot's name nor the squadron- his initials are A. B.   It has the 8 grommet vent, Made in England DOT zipper pulls with 1 replacement pull that has AM   ( Air Ministry )   Can anyone help with this insignia so that I can sell it ?    

Very nice DUI in good condition, is it a sterling variant as well? I believe I noticed your post on 743 tk bn FB didn't I?

The tracking option on Ebay says only Fargo and West-Fargo.

OCD = Office of Civil Defense. I think these were used from the WW2 era into the 1970's.

RemiFX, where was the pin shipped from?

Definitely!

Hello, I got this helmet yesterday.  They said it was a civil defense helmet.  Any history on these?  When were these used? Thanks John

The box appears to be from an American Red Cross Woman’s Service Pin.