I am putting this out there for our uniform experts. He could well be wearing the 1884-pattern infantry uniform coat or perhaps a militia version of the 1884-pattern enlisted coat. Next question is that aigullettes (the cord over his shoulder) that he is wearing? Next question is, does his forage cap have a color band around the bottom? Is this a model 1871-pattern forage cap, perhaps with a 1883-pattern officer chinstrap? Does the forage cap have a 1885-pattern enlisted wreath badge on it with "GBS" in the wreath?
If we can answer the above questions, we could well be on our way to deciding the general year of this image, and if this is a militia uniform. At this point I am leaning towards militia in the mid to late 1880s, perhaps a bit later. Could "GBS" mean G? Student Battalion, G? Service Brigade or Battalion?