Raphael Dressler (1784–1835) was a well known performer and teacher in London from 1820 to 1834. His flute method, New and Complete Instructions for the Flute is Op. 68 of over 100 works, so I imagine the original publication was circa 1825–30. There are 55 pages in my edition (published by E. Riley, NY). It is perhaps not so informative as the methods in English by Nicholson, Drouet, and Lindsay from about the same time, but still useful.
W. N. James praises Dressler's performance and compositions in the short section on him in his A Word or Two on the Flute of 1826, and based in large part on acquaintance with Dressler, James observes:
The German performers on the flute are peculiar in their style of playing it. The tone which they produce, —the fingerings which they adopt, —and their love of niceties and technicalities, —are widely different from the French and English schools. .... While many a worthless, superfical writer will gain popularity by concocting and disseminating the most worthless trash, —the German, the true musician, who has an intrinsic knowledge of the meaning of every note that he uses, is suffered to lie in neglect.....
Dressler also spent much of his career in Vienna before settling in London, and I hoped to discern some Viennese influence or learn about the above mentioned peculiarities of German performers from the method. But in addition to his preference for an 11-key flute with a low b rather than the common English 8-key flute, I can only point to his use of Quantz-like articulation syllables and his dislike of what is probably a Nicholson-like intense sound on the low notes.
He says that "During the last twenty years the Flute has been so much improved, that, from being the most imperfect of wind instruments, it has been rendered the most perfect." This due to the invention of the additional keys.
Dressler says that it is regrettable that there is not a standard number of keys, some performers using four, some six, some eight, etc., but that he finds his extra keys indispensible, except perhaps for the low b. The two other keys on his flute were an extra Bb lever and a third F key, he says. I wonder where that latter key was. The diagram shows only a 9-key flute, the ninth key being the second Bb.
He does not describe the tone he desires at great length, but he does mention "There is a kind of tone resembling the Horn, produced on the lower part of the instrument...", and this he condemns.
The fingering chart contains no surprises. The main fingering for c'' is -2-456K, just as for c'''; alternates include use of the C key or as a harmonic of the c', but never -23---K. The D# key is to be raised for almost every note, including e' and e''. The F key is to be raised for the f'# and f''# in slow tempos. There are many alternate fingerings given for notes at the top of the 2nd and into the 3rd octave. One can surmise from some of the high fingerings that he did not play a large-holed flute.
The Bb and C keys for RH1 were primarily used for trills, but were also useful in passages where Bb or C was the high note.
Dressler does not explicitly mention sensitive notes ('notes sensible'), but some of the fingerings he gives for passages show that he didn't mind narrowed semitones. E.g., he recommends that a c#'' between two d''s be played with the low C# key.
His illustrations of how to play appogiaturas include the example of two quarter notes descending a third, with an eighth note appogiatura from above to each. This he says is played as: eighth note, 16th note, 16th rest, eighth note, 16th note, 16th rest. Similarly, two eighth notes descending a third with appogiaturas from above to each are played with 32nd rests. I liked seeing this in print, as it is a performance practice that I am fond of, when used appropriately. Thomas Lindsay, in his method of 1828, does something similar: he indicates that in passages of eighth notes slurred in pairs, the pairs may be played decrescendo with the second of each pair shortened to a 16th note and followed by a 16th rest. "...Much of what is called style, depends upon the qualified application of this very simple principle", Lindsay says.
"The small character [a small 16th note or an 8th with a slash] is also used to represent a very short note before a principal note...," says Dressler. But no written out examples are given. ("Before a note" does not necessarily mean "before the beat".)
Dressler shows the trill as beginning with the main note, but as soon as he has made the idea clear he says "It may be started in different ways; with the principal note itself, with the note above, or with a turn written in small notes."
There are very short sections on glides and harmonics. He does not mention vibration (or any other kind of vibrato).
His basic articulation syllables are 'too' and 'doo'. Double tonguing is done with 'tootle' or 'doodle', and, e.g., in one illustration, 'doo toodle loodle loo'. For dotted notes we find 'dootoo rootoo rootoo'. For "smooth and plaintive melodies", Dressler recommends at least ocassional use of 'hoo' (no tongue).