While I doubt they let the film people use one of Fritz' rl flutes (aka the one still on exhibition in Sanssouci), my guess is that they did go to the trouble of having someone create an accurate reproduction. As far as I recall, the size fits what I've seen from this kind of 18th century traverse flute. (Hence the need to take the flute apart for transport.)
Re: Arno W. as Fritz - I know what you mean. :) The gauntness can be handwaved since an icon doesn't say this is before and early in the 7 Years War, not in the later stages and after when he actually was gaunt, and his tallness comes across when he's next to other people, which except for the Fredersdorf one he's not in the icons.) (Otoh you really see that the Italian greyhounds were pets, not hunting or attack dogs, definitely small enough to be put under one's coat in the winter...)
Re: Sachsens Glanz und Preußens Gloria: PICSPAM
Re: Arno W. as Fritz - I know what you mean. :) The gauntness can be handwaved since an icon doesn't say this is before and early in the 7 Years War, not in the later stages and after when he actually was gaunt, and his tallness comes across when he's next to other people, which except for the Fredersdorf one he's not in the icons.) (Otoh you really see that the Italian greyhounds were pets, not hunting or attack dogs, definitely small enough to be put under one's coat in the winter...)