Glad to help. I am not sure that is Marx in the pic, but given his age and the fact that he is the only officer, it is most likely him.
He is actually wearing a Feuerschutzpolizei hat in the pic, which differs from yours in that the body is mottled green wool, with a black wool band. This change-over occured in 1938-39.
You great-uncle must have occupied Herr Marx's house in '45!