From the Wonder-Bread loaf shape, battery box and Doughboy rear vent, Its definatly an Avion.
Patina and vent placements, would sugest a 1963-1965 Sportsman 18'.
Can't polish it, its anodized. But definatly worth dragging home and cleaning up.
I might even bet a 6 pack of Henry Wienhart's that the floor is still good.
see page 10 of this brocure:
http://www.silveravion.com/downloads...rochure_sm.pdf