An 1873 5 barreled Nordenfelt gun is up for auction online at icollector.com.  This original gun was captured by the U.S. during the Spanish American War. The gun appears to be in Spanish 50/70 caliber.  The octagonal barrels are blued and there are internal parts missing.   Bidding starts at 10 grand USD, and there are 5 days left as of 4/25/10.

Update: This gun  sold for $20,000 USD

nordenfelt 5 barrelled gun