The first mentioning of the famous "Oh du lieber Augustin"-tune, which is prominently featured in the movie and are sang by Augustin himself, are recorded in 1788, over 100 years after the movie's Setting. Also in the movie it is presented as a composition of an unnamed Emperor, while the original Composer is unknown.
Augustin is seen playing a Lyre-Guitar, which was invented in the late 18th century, 100 years before the movie's setting.
A courtier says to the Kaisre that his Music is very "popular". The German word "Populär" came into common German language in the 18th century from the French "populaire" and was originally more a public word, so it is very unlikely it would have been said by the noble Group.
Augustin mentioned the term "Hartschier", as the members of the residence guards of the Duke. While the term existed since 1669 in the German language, it was more common in Bavaria for the "Hartschier-Garde" of Fredinand Maria of Bavaria. In Austria, where the story takes place, a similar sounding Name, "Arcieren-Leibgarde" was more common.