Below a picture of the original 3 part Naust in the museum in Berlin.
Below a picture of my first copy of that flute and the only thing I need to say is that for me it plays fabulously.
Further information on Naust can be found on the Naust
Frankfurt: Naust F page
The cap on the original is not original and I used measurements of the cap of a different three part original Naust. Looks better I think.