There are different dates to be found:
Protos Typ C1 10/30 PS (1914-xxxx) -> Halwart Schrader, Deutsche Autos 1885-1920
Protos Typ C1 10/30 PS (1913/1914- xxxx) -> Hans-Heinrich von Fersen, Autos in Deutschland 1885-1920
Protos Typ C 10/30 PS (1913-1924) \
Protos Typ C1 10/45 PS (1924-1926) / -> Paul Gränz, Peter Kirchberg, Ahnen unserer Autos
Protos Typ C 10/30 PS (1913-1914, 1918-1924) \
Protos Typ C1 10/45 PS (1924-1927) / -> Werner Oswald, Deutsche Autos 1920-1945.
If it is not the 10/30 PS I have an idea what else it could be. Is it still locked?