M.A.V. I di Salvinelli Folding Companion 28Ga. Single Shot Shotgun.
This shotgun was made in Italy and imported by Dakin Gun Company San Francisco-USA. They were also sold by Beretta and Galef. These guns in 28ga are very rare.
It also just goes to show me. That even after 50 years of shooting that there is ALWAYS something new to learn about guns. As I had never even heard of this outfit before I saw this shotgun!