Originally Posted by
Rutan16
AZNZ was a United build frame that they got rid of very early for some reason.
Most of Britannia's 737-200s were built to their own '204' specification. BGNW was a -219 which arrived via Air New Zealand/NAC. BJXJ was from the same source ultimately but Britannia acquired her from Dan Air. BOSL and OSLA were both - 2U4s, both built for Owners' Services but technically identical to Britannia's own Advanced -204s.
The Civil Aircraft Markings books in the 1980s used to flag up the Britannia ADV models in the type description, whereas the early birds were simply listed as -204. But I can't quite remember which was which.
I would venture that all the other British-registered 737-200s were, at that time, the Advanced models so highlighting this was unnecessary .