[Tomislav Haramincic]

The two plates caused a lot of confusion in the past. As Mike and Artie already explained, the G-10 was a new built airframe and it represented the last G model incorporating all the "improvements" of the previous models (G-6 & G-14).
The second plate on the Bf 109G-10 WNr.610937, with the inscription 109143G14U4 127914 is a fuselage subassembly plate. 109143 means 109.143 which is the Baugruppe designation for all G-6 and G-14 fuselages, and so very probably also for the G-10 because the fuselage shells are identical for all those three types. G14U4 indicates that this fuselage was probably made for the 51x xxx WNr-series bulit by WNF, but never got to the G-14 assembly lines. 127914 is just the fuselage subassembly number. The simplified subassembly plate is characteristic for the late WNF production.
IMHO, this fuselage was just one of many preproduced fuselages and other subassembly parts that weren't used immediately on the assembly lines, but when the production changed to G-10's the preproduced fuselages (as they are the same) were normally used for further production.
So this G-10 hasn't got a used G-14 fuselage, but a brand new fuselage which was only intended for the G-14 production.
The Änderungsstufe plate was added to indicate subsequent changes that might appear during the operational use of the aircraft.