This is a Savage known as the Renegauge chambered in 12 Gauge 3", model 57604.
Savage produces purpose built firearms that come out of the box bristling with special features you won't find from other manufacturers. Whether you use them for recreational or competitive shooting" self-defense or hunting" Savage products are designed to give you an edge.
Features:
Semi-Auto
Polymer Stock
Interchangeable Chokes