I follow old Conoco gas stations and I looked through a lot of old photos of the M&S 80. The best I can tell is that Conoco used these pump top signs in 1953 when they introduced Super gasoline "with TCP". I am attaching the best two photos I can find and you can see in one photo the rods used to support the sign. They actually look to sit on top of the pump and I don't honestly see a single shaft descending into a center hole. What is clear from looking at my many photos is that these pump toppers were used for the introduction of Super and they seem to be only placed on the Super pump....which would be the first use of the ad glass on the M&S 80 by Conoco in 1953.