SAWMILL. Quarter plate Tintype. My guess is c1870.
Although fairly damaged by corrosion and other suface degrading, this is still a fascinating image. I beleive this is a steam driven sawmill. It's very unusual to find a closeup of a sawmill. Most often, tintypes and cabinet cards of sawmills where taken from a distance. If you look closely, you can see three men standing in front, a ladder set at the roof, and a large length of wood ready to be milled.