This is a classic tintype from the Civil War. When these were made dark lacquer was used as support for the photographic emulsion. They have a tendency to get darker with age and this one is no different. For as old as this is and the size there is still quite a bit of detail there. The emulsion has broken down over time. There are actually hundreds of pin holes in the surface of this image some filled with dirt that can be seen on the high-resolution version. You can see the edges where moisture has gotten under the emulsion and it has broken down and is flaking off. Another interesting thing about is image is the retouching that was done. The belt buckle, chain (below the rifle) and brass buttons are hand painted in. Typically, we spend the most time on the faces when we restore images and let the edges remain in the state, we found them in.