Civil War Salute Cannon

I have been told that this item is a Civil War Salute Cannon.  It was unearthed about ten years ago, approximately 15 feet underground across the street from St. Vincent's Hospital in Manhattan, NY.  It is small and heavy. Approximate dimensions are 28" long x 16" wide x 15" high. The barrel, wheels, and sides are all metalish, and the barrel sits on wood.