There are supposed to be a couple of washers, a spring, and a nut on the “rusty stud” below the bottom of the vent window frame. The washers are splined to be located properly on the stud. These keep the vent window from spinning around. I would suggest contacting one of our parts suppliers (Big M, Macs, Mercuryland). This is not an uncommon part as I believe ’52 thru ’54 had the same vent window.