The Zuckerman helmet was a high domed, mild steel helmet that civilians could purchase and that was also allocated to fire watchers and fire guards. The design allowed the helmet was to withstand debris hits by denting and thus protecting the wearer.
As the below document from the Ministry of Home Security shows, there was a front to the helmet. However, many photographs from the war show people wearing the helmet back-to-front. Probably not much of an issue if the helmet saved your life either way round.