When we say a part is unfinished brass it means the brass is in an natural state after manufacturing. Nothing more has been done to the brass to finish it. The brass is dull, may have manufacturing marks such as small scratches or scrapes. The brass could have manufacturing oils or grease. This can stain the brass in some places. The brass can be tarnished. After manufacturing, when brass is not sealed with varnish or lacquer, oxidation can start darkening the brass. Since parts are manufactured at different times unfinished brass parts can be at different states of aging. This would make unfinished parts not match each other. Many people use unfinished brass parts as they are to give an old antique feel. The parts continue to oxidize and eventually match each other.