National Insurance Number from 1980s

Hi, My mother in law worked in the UK for about 12 months back in the 80s and unfortunately she cannot find any payslips or anything related to her NINO. She needs it in order to prove that she worked here for a while. We have submitted request to receive the NINO via post but HMRC has said that she doesn't have one. I guess it must be something to do with the fact that back then everything was stored in a paper archive? Has anyone done anything similar or knows which way would be best to find out her NINO? The company she worked for is also dissolved so she cannot ask anyone there. Thank you, 

Name removed admin .

Does she know a colleague who worked for the company at the same time? If yes, ask the colleague if they can find a P60 or a P45 - this will have the employer's "PAYE reference" (usually in the form of 123/ABC456 or 123 ABC456). This may provide further information to link your mother in law to her NI number.

Hi Marco,
When your mother-in-law started working in the UK, she would have been advised to register at her local DSS (as they were known at the time) Office to apply for a NI number.  
A National Insurance number is not proof of working in the UK.  
Since the introduction of the National Insurance Recording System in 1975 all records after that date are stored electronically.  
It may be that she did not earn enough to pay NI and in which case she may not have even been advised to apply for a NINO?  
If your mother has any evidence from her employment in the UK ie. Wage slips, P60,P45, Contract information, she should send this in with as much detail of the employment as possible (employers name and address, staff/payroll number, period of employment, weekly/monthly wage received etc. to help us trace any NI she may have paid.  
If she has evidence that she did pay and we are able to trace them, we can ask DWP to allocate a NINO and have the NI paid transferred to her new NINO?  
She can write to Individuals Caseworker, PT Operations North East England, HMRC.  BX9 1AN.
Thank you.
 

Thank you both for your help and valuable advices. Unfortunately she has no documents from that period which makes it virtually impossible to refer to any useful information. She has a friend who worked in the same company for 5 years so she might be able to get some of the information from her. We will see what we can find and check again. Thank you again for your help. Marco