In this case, it is a part number for the nacell only.
95% of all werk numbers ranges are based on orders placed, and actual documented losses - not on the specific werk numbers made. I have never actually seen official documents from any wartime manufacture that states, "on this day we made werk # "X", and it was complete, transferred to unit "X". There are numerous wrecks from various aircraft being found where the main werk falls "outside" the werk number ranges that are documented, as well as loss records.
Which documents are you referring to specifically?