I believe this signed artwork is an early brush and ink drawing by Hans Gassebner of Germany. A quick search of the German wiki gives a brief overview of his sad and somewhat tragic life. Gassebner is considered

'...a German Modernist painter. As an artist, he is assigned to the "lost generation". Between 1923 and 1933 he stayed in the art centers of Vienna..., Zurich, Berlin and Stuttgart. With the beginning of the Third Reich, Hans Gassebner was declared a "degenerate artist". In November 1933 he emigrated to Yugoslavia together with his Jewish partner and her daughter. They lived in extremely oppressive financial and spatial conditions.' (Wikipedia)

This drawing is on a thick piece of felt-like paper that measures 14 inches by 10 inches. The paper is brownish-tan, and is fairly clean. There is some wrinkling in the upper left corner, and a small tear in the lower right corner (see closeup photos). The drawing itself is nicely defined, with no wrinkles or tears.

I believe this is an ink & brush on paper because the black ink is thicker in some areas (like the jacket), and has a wet look when I hold it up to the light. The piece has a pencil signature in the lower right corner, and what I believe may be a date for 1924. On the back side of the drawing, someone has hand-written "Hans Gassebner | Man in Vienna Prater" in what looks like a crayon. The caption, "Man in Vienna Prater", I am guessing, may date to the time 1923-33 when Gassebner was in Vienna.