BA Internal Config codes seem different from all those above (including 77C)
77Z - 777-236ER (Rolls Royce Longe Range model with 12 NF)
77Y - Standard 777-236ER standard B market (mostly no AVOD GE Engines 14F)
77J - 3 Class (no First)
77G - 777-300ER
77X - 777-236 GE Engines original 3, Labelled A Market (ZZZ registrations)
Strange