The LNER Encyclopedia

I took the attached photograph at Stratford depot in May 1979. Can anyone identify the type of coach please?

I would tentatively suggest it could be a Dia 115 Corridor Third showing the corridor side. If it is then it has had an additional door added and what appears to be a toilet window would have been a full size window teh same as the rest down that side. Shame we don't know the departmental number as it could be traced on departmentals.com website.