It's not from the Civil War. It's a soldier cast from a mold made by the Schneider Brothers in Leipzig, Saxony, Germany. They were in business from around 1890 until 1945. They made molds for hobbyists to cast their own toy soldiers at home. Their molds were sold here in the US in the 20s by several reps. Henry Sachs was the best-known. Their molds triggered the growth of several American mold makers, who started out selling copies of the Schneider molds, then developed their own.
This particular figure, when complete, depicts a German artillery officer, sighting his field piece.
In that condition, it's real value is for melting down and making new figures. It's not rare, and the molds still exist to cast this and many other Schneider figures.
Prost!
Brad