A complete working 37mm Hotchkiss Revolving Cannon is for sale at the Cannon Superstore. The price is $95,000 and is an original 1880 gun (the ad says four barrels but I count the usual 5. The carriage is a reproduction.

pic of cannon

Rare Hotchkiss Revolving Cannon sells for $92,000 at Rock Island Auction Company auction in Moline, Illinois last December. The gun sold was a naval cannon on carriage mount and included accessories.