The standing collar, the double row button unfirom and the cap points to an Imperial Russian naval unform. However, most Russian uniforms of the era includes rank insignia on the shoulder, which his uniform does not.

The beard indicates a post-Crimean war and pre-ww1 era, which fits with the cap.

The Bulgarians and Germans wore similar caps. Do you have any knowledge of his nationality and the decade when the picture was taken? It would ease identifyin the photo a lot.