Sign from an ARP (Air Raid Precautions) post. The Air Raid Wardens working from the post had the job of trying to get people to shelter during enemy air attacks, and enforcing black-out regulations. The coat-of-arms with 3 daggers represents the county of Essex in south-east England.
Practically everyone in Britain carried an Identity Card like this during the Second World War. Here you see the front and back of this vital document.
Red Cross armband.