Let me first simply copy the Kirst description from the New Langwill index .
Kirst, Friederich Gabriel August, (not completely sure) Born Dresden 1750, Died Berlin 29 April 1806. Flute maker in Potsdam from 1772 to 1804. Probably son of Johann Georg Kirst, inspector of municipal waterworks in Dresden. Apprenticed to A Grenser, Dresden 1768/1770. Working for C.F.Freyer in Potsdam. In 1772 he married Freyer's widow after Freyer died and took over his workshop as master. In 1772 he was also granted 'privilegium privatum' to supply the entire Prussian army with woodwind instruments. Nicolai (1779) reported that flötenmacher Kirst (im Holländischen Revier) bekommt Gehalt vom Könige (woodwind instrument maker Kirst (in the Dutch quarter)receives a salary from the king). There were a number of apprentices in his workshop; J.G. Martin, I.C.H.Müller, A.F.Piering and J.W..Weisse. In 1804 the workshop was taken over by his stepson J.G.Freyer, this changed later to Freyer and Martin. It is most likely both from the extant instruments and form the fact that the workshop was in Potsdam that there was a cooperation between Kirst and Quantz.
So far a slightly reorganized copy from the Langwill index.
There are four Kirst flutes in the Utrecht collection. One with more keys and three one keyed kirsts. They are all difficult with respect too intonation. I have done some work to correct this and my copies now have an excellent intonation. I believe that 300 years ago this also must have been the case.
This is a powerful, very open and dynamically flexible instrument. The original also has 440 and 430 joints. It is a classical flute, probably around 1780. It is very flexible dynamically and has a great third octave.
 The New Langwill Index. Tony Bingham London, ISBN 0-946113-04-1