The sticker was generally located in the lower corner of the passenger car windshield as you mentioned. I believe it was permissible to put the sticker in the top of the windshield also ...but the lower corner was commonly accepted. Gas rationing was actually to ration rubber which was the commodity in short supply. You likely have an A stamp which was most common. You might do a search for WWII Gas Stamps ... it was a fasinating time of stamps, blackmarket sugar, with everyone seemingly in the war effort.... I am so glad that I was a part of that time.