The letter, dated in the mid-1700s and reportedly written by Leopold Mozart, has an ink fingerprint on it, according to Salzburg historian Christian Moser.
Only about 20 examples of Leopold Mozart's handwriting exist, making the letter itself a significant find.
Another group of scientists in Salzburg is trying to determine, through DNA testing, if a skull in the collection of the International Mozarteum Foundation is that of the composer. The skull came to the foundation through unspecified channels; a gravedigger reportedly retrieved it from the pauper's grave in Vienna where the composer was buried.