I was nosing round the late Joe Baugher's site and realised that USAF/US Army serial sometimes now reflect the manufacturer's MSN or line number; eg: CH-47F 15-08462 is MSN M8462 and C-130J 14-5810 is MSN 5810. It seems the days of giving the next batch of airframes ordered serial numbers consecutive to the previous batch of a different type ordered under the fiscal year are gone.
MoD seem to allocate batches all over the shop in the latter Z* sequence, again it used to be a fairly orderly transition from say XZ100 to XZ999 then ZA100 to ZA999, etc, now one type might be ZZ***, the next ZM*** - or so it seems. Confoosed...