Can someone tell me what this helmet is and from what period?

[ShackleDragger]

Look pretty recent, but don't have a clue:

[Adrian Stevenson]

Search "Zuckermann"

Cheers, Ade.

[tinlid]

A civilian protective helmet, mostly dated 1941 but a few were made in December 1940.The M might be for Messenger, either for the fire guard as these helmets were used a lot by them, or if bought privately by the person who owned the helmet for whoever he / she worked for in the ARP.

[ShackleDragger]

Thanks for the help guys, much appreciated!