Hi Grzegorz!
The link you provided has wrong information.
For many years, it was thought that older G-6 airframes and G-14 airframes were used in the production of the G-10.
This is not the case, and was dis-proven around 4 years ago.
The G-10 was a "completely" new airframe, top to bottom, and no G-6 or G-14 airframes were used to "upgrade" or build to G-10 status.
I do agree with you ArtieBob on the previously made parts, fuselage, etc. being used in construction, but it would not solve the mystery of the 2nd data plate....I'll explain why.
The WNF "DIANA" plant (which only manufactured the G-10/U4) is a perfect example. Fuselages were completely newly-made in tunnel 217A; tunnel 217C manufactured newly-made wings, and 217B made wing components. The aircraft was then transported for final assembly at the railway station as Tisnov.
The only assembly made OUTSIDE of the plant were the tail surfaces (rudder), which were of the wooden type and once manufactured, sent to the plant for assembly.
Everything on the G-10 was made new in it's entirety, and no G-6 or G-14 parts, sub-assemblies, or fuselages were used in the construction...yet machines were found at DIANA (after the surrender) had this 2nd data plate.
Also, my concerns on information in the web article provided above are as follows:
610824 had all data plates removed, and none of the information which was on them was recorded...only a note on a sub-assembly plate which was found inside the aircraft. What was on that plate, no one knows...but the claim was that this subassembly piece was made for the G6. What that piece was, no one knows. It could have been a field replacement of any kind kind. In mid-1944, WNF was only manufacturing then G-14/U4, so having a G-6 Fuselage of any type lying around in Jan/Feb of 1945 when 610824 was built is an impossibility, no?
Also, it is noted that 610937 had plates in-tact, and suggest the machine was a re-built G-14, werke number 127914. However, I have checked all my sources, and NO G-6 or G-14's were allotted a W.Nr. even close to that number. There is a gap in G-6 production from W.Nr. 110500 to W.Nr. 140400, and nothing was made in between...G-14 production began at the W.Nr.165000, ruling out "both" G-6 or G-14 airframes being used or upgraded. Please someone correct me if I am wrong on this, as I am only sourcing 2 books on the werk. number production.
I suspect these data plates that were found, were not werk numbers of the aircraft, but rather werk numbers of the part in question.
There are some instances and 1 or 2 photos that show older tail surfaces (small rudder), elevator, even a completely older tail, on the G-10 (different camouflage pattern), but after thorough examination, it was proven that these were done to get the aircraft flyable (in the field) to make the surrender to Neubiberg (American side) and escape the Russian Advance. And I think there were only 2 aircraft which had this done.
Various G-10's constructed at WNF DIANA (which made all aircraft new), had this dual tag (found after the German surrender). So that disproves the theory of an older Fuselage (G6 or G-14) being used in the construction, and the reason for that data plate.
I thought the tag "may" have been for field use (entering dates or changes when a major assembly was replaced in the field), but if that were the case, all aircraft would have had dual tags, which is not the case.
hmmm...