Whilst there are numerous enamel badges in existence, there were also many cheaper celluloid button pin badges produced earlier in the war. Many were given to personnel involved in manning large ARP shelters - such as Shelter Marshals and Key Men. Others appear to have been given to people to allow access to the shelter - they are numbered. There were badges for Fire Wardens and ARP Wardens.
News about interesting insignia, ARP related info and period photos that turn up.