The correspondence comprises letters, circulars to other parish ministers, one postcard showing Althaus with Sinti and Roma children, and one copy of Der Sonntag, a Lutheran Church newsletter for Brunswick and surrounding.
The material documents Althaus’ conflict with officials from the Lutheran Church, which included disciplinary actions against him and attempts to have him retired early. Moreover, it sheds light on his long-term association with Sinti and Roma, mainly survivors of the Nazi genocide ('Porajmos'), who had settled in the nearby town of Hildesheim. Althaus' activities contained relief as well as missionary work. Additionally, the correspondence contains one letter to a person named Hans-Ludwig Althaus.