This is an original  WW2 Martin B-26 Marauder Bomber Upper  Martin Turret Amplidyne Motor. It is labeled 5AM31NJ18A as best as I can read the label. The cannon plug connector is not perfect but still works.  It is 12 x 8 x 7 inches and weights 30 pounds. The B-26 Marauder is a medium range bomber. The bomber saw lots of action in both Europe and the South Pacific. Today there are no B-26 Marauders currently still flying. The Smithsonian Air & Space Museum is in the process of restoring the famous Flak Bait. That aircraft has more combat missions than any other  bomber.  This item is being sold as a collectable. Buyer to pay actual shipping.