Quite a nice piece here by Dupre from his 24 inventions.
It says D Major but how long it truly stays in D Major is probably the first three notes... another one full of accidentals.
The registration calls for Flutes in both hands. So one hand has the Swell Rohrflute and Flute Dolce and the other has the Choir Concert Flute. The two manuals later get coupled together near the end.