I think the original question is valid, sidepulls were the originals which eventually gave way to centerpulls. EVeryone copied the MAFAC design, even universal introduced a centerpull in the 1960s (but maintained a sidepull model also, the universal extra).. in anycase, by the early 1970s centerpulls were a thing of the past on race bikes but continued to appear on entry level and lower end bicycles into the 1980s... one place centerpulls should ALWAYS be used is mixtes. They were made for sidepulls, anything else just looks wrong.