1931 Paul, when Signal bought the chain of stations from Universal gas stations there name for gas was purr-pull and Signal used that name for advertizing, because it was dyed purr-pull, but later on Signal had three types of gasoline, Signal Ethyl, Signal Anti-knock , and there very cheap Peerless, the picture on my website isn't very good but it shows all three at a grand opening in Sacramento,Ca. in 1941. so around the 40ties you still had a lot of model T's and A's running around that couldn't use the hotter gasolines. hope this helps a little.