X = black steel wheel for the spare if the car full wheel covers. With "dog dishes" the spare would have been the body color of that car. Red would mean a Redline F70 ("14 or 15") tire on whatever color spare. Not sure what spare came with a car with "road wheels/Magnum wheels"??? One '69 sales film had an A4 GTX with road wheels and what looks like a silver road wheel spare in the trunk. I know that on the Lynch Road A12 trunk writing the X = black steel wheel, only G 70 15 redlines came on the A12's, (well for the most part, have seen OE white walls rare.