Duplicated Werk-Nummer blocks

[Seaplanes]

During the mid 1930's some aircraft delivered on RLM contracts to the Luftwaffe had duplicated Werk-Nummer series for the same model and sub-type. This is for example the case for two different series of the Heinkel He 45D. One series with W.Nr. 707 to 746 and accepted by BAL (Bauaufsicht der Luftwaffe) from February 1935 to August 1935 was duplicated with another series with W.Nr. 707 to 746 and accepted by BAL from July 1935 to January 1936. For practical reasons, the second series were delivered with W.Nr. written as 2/707 through to 2/746. The problem came later towards 1940, when one did not bother to differ between the two series resulting in that two aircraft could be operated within the Luftwaffe with different units but with the same W.Nr. and both as He 45D aircraft. As this was by no means the order of the day, it did happen quite frequently. To complicate the picture even further, I have even noticed triplications of W.Nr. If some of you have problems with two different stories of Luftwaffe aircraft but with the same W.Nr., it may be that one of them should have its number written with a 2/ or perhaps 3/ in front of the W.Nr.
I would love to have opinions about this ,as I can not remember to have seen this problem being discussed before.