The beauty of a box-magazine-fed pump-action is that it negates several of the traditional pump-action's advantages while simultaneously providing you with the shortcomings and weight-gains associated with separable magazines, all without any improvement in magazine capacity.
That one is Russian, and I think there was another manufactured in either Europe or South Korea. A US company used to make conversions for Remington 870's, but for reasons that continue to mystify, no one bought them.