Fw 190 engine number

[stephen f. polyak]

I am not positive, but I suspect this is a main (Werk-Nr.) identification plate from a BMW 801 engine…

http://fw190.hobbyvista.com/woods2.htm

My thoughts… I can imagine that when a new aircraft left a factory, particularly during the first-half of the war, reliable records existed that showed the engine and airframe pairing by Werk-Nr. Such links may have also followed an aircraft/engine in the form of service and maintenance records, while engine swaps over a plane's operational life added detours. Over time, production accounting practices likely deteriorated, field records were probably not always kept up with, and in the end, the various records were almost certainly destroyed, lost and scattered. (Perhaps something is buried in an archive?) So if you happen to know an engine serial number, that's about all you will know, versus it being a reliable pointer to the specific aircraft it powered.