United Kingdom - Passport & Nationality - British Citizenship by Descent (UKM British Registration)
A person...
1) who was born between 01.01.1949 and 31.12.1982;
2) whose mother was registered as a British citizen before 31.12.1982; AND
3) who was born AFTER their mother's registration but BEFORE 31.12.1982.
... may have a potential claim to British nationality. Their mother's registration as a British citizen meant that she passed on a CUKC by descent status to their child, and the child could have been reclassified as a British citizen on 01.01.1983.