Are you still looking for a 1928 Pontiac Radiator Cap? It was my dad's. He worked his entire career at GM as a design engineer. From my research, I don't know that I have seen one in better condition than this one. I am kinda wondering if it is actually 1930-31, based on it's characteristics. Please feel free to reach out if anyone is interested in making an offer. karen.piotrowski@gmail.com