This poetic portrait makes me think of James Joyce, not just for the spectacles and mustache and sensitive looking face of the subject, but also for the moody manner of the painting, with subdued palette and that shadow on the wall evoking a sense of a haunted interior life. And yet the pink rising high on his cheeks surely signals great passion, and great things yet to come! I believe the portrait is German, with a note on the back that I believe describes the subject as a Carl Jaeger; there was a German portraitist Carl Jaeger, 1833-1887, but I am doubtful that this is meant to be him--and would guess this painting dates to the 1920s or so. 

16 1/2" x 14 1/2", oil on board (with some surface texture) and in worn condition, with general scratches and dings to the surface as evident, which I personally like as they enhance the already moody painting's sense of aura. One nail hole at center top, a little fraying to the board at lower left and some minor warping as documented.