"Trap" mirrors were standard (drivers side, right side dealer installed option) through 1973. Officially the "Flag" style mirror was to be used for 1974 on, along with the federal bumpers, turn signal lever moving to the left, etc. However like all automotive assembly lines, some trap mirror found their way onto some later cars to use up the inventory.
Mounting was a pot metal bracket screwed onto the door sheet metal with a type of blind nut. Then the black gasket was fitted to the mirror and the mirror was attached to the bracket with a single set screw from the rear, being covered by a flap on the gasket.
I have left and right on my 1973 ever since delivered to me in July, 1973. Those are a nice find. If you don't want to use them, Im sure they will bring big buckes on auction.