Hi
Some math's you done there
Also to take into consideration, is that some very early Air Arms models were put together with Sussex Armoury Parts. So serial # could be from mixed parts, and proper sequential order would be hard to ascertain in the transition period.
Though I Reckon I'm thinking too much into it.
What is interesting though is that I must have a very early Camargue & a rather late Hi-Power in my collection
Regards
Paddy