It is hard to imagine IUPAC without the Periodic Table, and in turn, without atomic weights. As IUPAC celebrates its centennial, its oldest body, the Commission on Isotopic Abundances and Atomic Weights (CIAAW) turns 120. The parent Commission was formed in March 1899 and its inaugural task was to decide the atomic weight standard: should it be based on hydrogen or oxygen? Although the issue was settled in favor of oxygen, when the CIAAW formally joined the IUPAC in 1919, the question of the atomic weight scale was back for debate suggesting that many issues before this Commission transcend their scientific merit. In fact, many view the Periodic Table and changes therein as a part of larger cultural fabric of science so any changes are likely to be debated for a long time.