You are correct- this soldier wears a 1902 enlisted man's dress uniform. The collar, shoulder straps, and the top edge of the cuffs (not visible in the picture) were piped in sky blue, as were the breast cords and flounders. The front closed with six buttons, with three on the cuff. Collar insignia, U.S. Cyphers and crossed rifles, were brass- and make this man's particular branch very easy to identify.

Unfortunately, this is almost all I can tell you about this uniform. The gentleman in the photograph wears no immediately identifiable regimental insignia, nor medals or ribbons. I hope this helps, nevertheless.