director: Arzén von Cserépy
year: 1925
country: Germany

Source notes
Bundesarchiv-Filmarchiv

Please verify date of film.
My father(Walter Lichtenstein) did Fridericus Rex in 1920, 1921. Regie arzen von Cserepy, mit Otto Gebhur.
Thank you
André Limot

The director is wrong. Arzén von Cserépy directed a Fridericus Rex-series in four parts in 1920-1922. With Otto Gebühr as main actor. (Gebühr played Friedrich der Große 10x in total).

The source notes from the Bundesarchive explicit cites that the 1925 movie is a one-parter. This could be only "Die Mühle von Sanssouci" by Deutsche Vereinsfilm AG, Director: Siegfried Philippi and - of course - with Otto Gebühr. Filmed in 1925, premiered on Feb. 1st, 1926.

The four-part movie by von Cserépy from 1920-1922 is not considered as lost. At least part 3+4 can be borrowed from the Bundesarchiv.

Here you find a list of Fridericus Rex Films as a start for your research.
https://de.wikipedia.org/wiki/Fridericus-Rex-Filme.