[Harold Lake]

Unless I miss my guess, airframe werknummern were NEVER changed for obvious reasons. Not to diminish the good folks at the NASM, but their conclusion that "640069" was the airframe's serial number was a hasty one. In checking, it appears NO Fw 190 A-7s ever used the prefix "640" and for that matter it doesn't appear that this prefix was used by ANY Fw 190 productiion batch. Few things aeronautical are ever cast in stone, but I suspect airframe werknummern may be one such example.