The crank itslef was from the 70's and the thought was that you would have more leverage in your downstroke if your foot was ahead of the crank arms rotation around the bb spindle. In reality it makes no differance as the space between the bb spindle and pedal spindle is the same and rotates at the same rate. Either way they look awesome and took me forever to track down. More can be found here. http://www.classicrendezvous.com/Italy/PMP_crk_ad.htm