Panado, one identifier you might find is the number of the Inspector who certified the final build of the flap. This may account for the 'A4388' assuming an Alenia inspector. Most BAe inspectors would be using a number of the for EEP NNN (as in English Electric Preston 123).
Insty66, industry preference was to change the part number for change in mod state as it provides better configuration control. Strike off mods were the preference of the Services (less work required) but in theory they should have only been used for relatively small configuration changes. Theory is one thing, expedience is another...
In general terms, all assemblies were designed with interchangeability (ICY) in mind so could easily have been fitted to many airframes throughout their lives.
EAP