1939 England and Wales Register

Does anyone else use this? I have access to it via Ancestry. It was puzzling me why late mother's maiden surname was crossed through and her married surname entered even though she did not marry until ten years later. Then I looked at the notes about the register and realised what an important document this was.

Extract from Ancestry:

Historical Context
Initially taken due to the onset of war with the purpose of producing National Identity Cards, the register later came to be multi-functional, first as an aid in the use of ration books and later helping officials record the movement of the civilian population over the following decades and from 1948, as the basis for the National Health Service Register. The 1939 Register is an extremely important genealogical resource, not only for the rich detail and information recorded for each person and household, but also in helping to bridge a thirty-year gap in census data. The census taken in 1931 was destroyed during the Second World War and no census was carried out in 1941 due to the ongoing conflict. The register, as held by The National Archives, contains data only for England and Wales and does not include records from households in Scotland, Northern Ireland, the Channel Islands or the Isle of Man.

Enumerators collected the data on 29th September 1939.

Redactions
Images have been redacted to protect the privacy of those still alive and we will be annually adding records for those with birth dates older than 100 years or if a record of the death has been reported to The National Archives. Images will also be updated to reflect the opening of the record. All indexes have been created from redacted images as provided by The National Archives and as such, some indexes may not include all information as originally recorded, where it is obscured from view.

War has been declared 26 day earlier. My grandmother is shown as an an assembler of ARP respirators as are many other people. I hadn't realised how quickly the country had responded to the threat of gas attack.