For an interesting discussion of Bf 109 Werknummern involving primarily export aircraft, plus conflicts in data from various sources, the reader is referred to the topic "Books on Bf 109 - 19" on the "References & Reference Materials" forum.
Specifically, related to the Sota-arkisto, Helsinki (Military Archive), commentary is made as to errors in the original Messerschmitt document "Übersichtsliste der Änderungs-Anweisungen BF109" which is a collection of modification orders and lists the Bf 109 (by WNr) which are affected by which modification (Änderungs-Anweisung). Subtypes covered are Bf 109 E-1 to early G-6.
Regards,
Richard