Question Author
There is an 8 figure number; Her married name, her address at the time and the address Ministry of Health, Insurance Dept, Blackpool Lancs. The reverse says 'The controller acknowleges the receipt of your application which is receiving attention' , so it is not an identity card, just a receipt with a reference number that needed to be quoted in correspondence. (There is more about notifying a change of address.)
This is not the question though. I want to know if it is possible to trace her details from this reference number as we are trying to trace her birth.
As for Ironmonger's reply, this is a six year search so far. We have all census relevant details (1891, 1901, after that she was in India) and an approximate birthdate, but not birth record, though we do have marriage certificate, and plenty of other family details. Several forums have tossed the question back and forth, but this Ministry of Heath card and ref number are a new find, therefore a new avenue I wanted to explore.