Appears to be a knit ribbed material of sorts... could be an overshirt or maybe even a sweater... not a uniform coat or sack. The buttons have been hand tinted by the photographer, so may or may not actually be brass. Nothing else present I can see such as weapons, leathers, canteens, waist belt, kepi or anything at all that would clue in that this could be a military related image... Otherwise at face value appears to be a civilian wearing a fancy trimmed sweater....