There was a picture of a quad in Bicycling! magazine's review of the 1972 Paris Show by Fred DeLong. It was on a SiNGER or some other builder's bike. They were a concept from a time in which the freewheels were just 5s. More useful gearing is probably obtainable on today's doubles with appropriate-for-the-terrain cogset.
Ken Wehrenberg, Hermann, MO