This set was unusual in the fact that there was an early series, consisting of the first 160 cards, and a second series of only 20 cards published more than a year later. I don't know whether this small number for the second set reflects its lack of popularity or something else. The original set was very popular, and it was a favorite of mine. The backs of the main set are printed with red, the favorite color of Topps in its 1950s sets. The backs of the second set come in two different series, blue and red, and I do not know the reason. The really exciting parts of the whole set were the unusual cars, including sportscars, racers, and European exotics. There is perhaps an excessive number of early cars, not all of which are interesting or notable.