marriage lines 
plural noun informal, chiefly British
A marriage certificate.Using birth certificates, archives and marriage lines John tries to understand more about the circumstances surrounding his birth and why he was given away....
- The registration of marriages and the issuing of ‘marriage lines ' to be held by one of the spouses, usually the wife, were important procedures for establishing status and the legitimacy of children.
- The coming local elections are well and truly a family affair, with seven husband and wife teams joined on party lines as well as by marriage lines to fight seats.