The Eichentopf flute is a single surviving instrument by the famous Leipzig maker, who also made all other woodwind and brass instruments. He is called the inventor of oboe d'amore and oboe da caccia as they were used by J.S. Bach in his cantatas and oratorios.
The original ivory flute has been altered drastically by shortening the joints and sockets and by closing the original embouchure and drilling a new one down the bore. Stefan Beck was the first maker who traveled to communist East Germany and did his research and reconstruction work on this flute. The original plays very well at 415 Hz, which is quit convenient for Neo-Baroque interpretations of 18th century music, but the proportions are not pleasing due to these alterations. It is quite obvious that the original must have been at a much lower pitch.
The flute has a relatively wide bore that doesn't have a strong taper but steps in the bore between the four sections, something not found in other flutes. Also it has a very special and early screw-cork in the head joint, which might indicate that the original had several corps de rechange and needed some fine tuning.
To me this is the ideal instrument to cover the German repertoire from 1720-1750. My flute is in ebony and plays at 410 and 400 Hz, which to me are the right pitch standards for Middle Germany in this period. It was not until August Grenser started work in Dresden, that 415 and higher came into use in the second half of the 18th century. Stefan Beck also offers different Eichentopf flutes to play at 415 or 392, that sound great and are easy to play. They are my first choice to recommend to students.
It seems difficult to cover more than 10 Hz with corps de rechange without compromising on the intonation. Eichentopf with his crew-cork made an important contribution to solve the problem. But it was not until decades later that Quantz build a head-slide and used a much wider bore and different undercutting to cover a half step, but never more.