(Note: Scale is approximate. Please check the exact measurements given under "Dimensions" to determine if this product is the right size for you).
Swedish 5-barrel mechanical gun, patented in 1873. The gun was invented by Helge Palmcrantz, but named after its manufacturer Thorsten Nordenfelt.
The gun would drop five cartridges at a time, one into the chamber of each barrel (gravity-fed, from the big box on top). The gun would fire by pushing the lever forward, then the spent cartridges would drop out of the bottom of the gun and new cartridges be loaded when pulling the lever back.
To the best of my knowledge, all five barrels would fire with each stroke. But they actually did it in sequence at intervals during the forward push,
not all at once like a volley gun*. However, I've seen videos where the gun is being fired, and it does sound more like a volley than a sequence of shots. Maybe there are different models? Guess you'll have to make your own mind up about it...
The Nordenfelt gun was used by, among others, the Swedish army and the British navy. The Nordenfelt gun is perhaps best known as a navy gun. This model, however, is a carriage-mounted variant intended for land combat.
1:35 scale version. 28mm scale version available here:
https://www.shapeways.com/product/962P7GAET/nordenfelt-organ-gun?optionId=244105619&li=shops
*
https://www.youtube.com/watch?v=zyG6vobtUeI