Trying to find meaning of an Immigration seal

This is about my mother. She has an old passport where the followings are stated on different pages:

Page 29. Visa Visitor 21st January 1971 My-mum's-name (hand-written)

Page 28. An Immigration officer's seal: Immigration Officer 5 FEB 1971 London Airport - Admitted on condition that stay does not exceed six months.

Page 27. A seal:
The condition attached to the holder's admission to the United Kingdom is hereby revoked.
Signature of the officer
for Under Secretary of State
Home Office
Date 18 AUG 1971

She came to the UK to join my father in 1971. He naturalized as a UK citizen but never applied for my mother. My parents left the UK in 1978 and never returned to live here (UK) permanently.

My father remembers that he also had similar seal on his passport and after getting that seal he applied for naturalization. I am not sure what was the rule at that time and it hard to find any information about the meaning of page 27 of my mother's passport.

My father thinks my mum received her residency when she got this seal on her passport. If this is the case, does it need renewal? If yes, how? My understanding is some one with ILR staying outside of the UK for more than 2 years may lose her ILR status.

So questions are:
** What does page 27 mean? Does it mean ILR?
** If ILR, is it still valid? Please note that after leaving the UK in 1978 she came back to visit only once in 2010 for 3 months.
** If ILR is not valid, is there a way to renew it?

My dad tried calling the local British High Commission. It is hard to get access to anyone there over the phone. He was asked to call a company that handles any visa application submission there. The company replied with generic web link from gov.uk about what to do if someone likes to immigrate to the UK.

I hope somebody can shed light on this. Thank you in advance.

ahmjt

i'd say yes, it was probably the antique 1971 version of the ILR (eg the stamp means she was now free from conditions)

then i'd say no, of courtse it is no longer valid, and i doubt there is a way to renew it

however if her husband is a british citizen, there is a way for her to re-enter as his wife, subject to all the new conditions, including financial requirement

that being said, what would have been the original basis for receiving the stamp? could she have some claim to right of abode in the UK through ancestry or past commonwealth citizenship? there was a change in the law on that in 1971

i'd need to look it up, or you can. however it is not entirely improbable that something happened in 1971 which created a right of abode or a right to register as a citizen for both of them, it may be just that only your father bothered to

in that case, whatever it was may still apply to her

if she received confirmation of right to abode, as i understand it never expireS

@sagareva many thanks for writing back. Your answer gave me more ideas to search for. I have started searching for 'right of adobe' and 'certificate of entitlement to right of adobe'. In a simplistic view my mum, a commonwealth citizen and married to my dad who has right to adobe, may be able to apply for certificate of entitlement. They were both living in the UK during 1970-1978 and working for NHS.

However, some of the things make me feel that it is not going to be that easy:
- My mother was initially a citizen of Pakistan, then became a citizen of Bangladesh.
- Pakistan left the Commonwealth in 1972 and rejoined later.

Anyway, all these are quite complex for me, so I have asked them to consult a local lawyer in Bangladesh who knows about UK immigration laws.