I first became involved in the history of quantum mechanics while I was on sabbatical at the Institute for the History of science in Berlin in the Spring and summer of 2008. I was fortunate to be able to join the core group at the Institute that met on a regular basis to read and discuss relevant primary literature. This was an especially fortunate circumstance for me as I was at the time translating and commenting on a paper from 1930 by Léon Rosenfeld. He was motivated to join in Zurich in 1929 one of the founders of quantum mechanics and quantum field theory, Wolfgang Pauli. Pauli and Werner Heisenberg, another of the founders, had proposed one of the first quantum field theories to describe the interaction of electrically charged matter with radiation. They were however not entirely satisfied with the manner in which they were forced to deal with the underlying gauge symmetry of the classical theory. Rosenfeld was invited to address the question, and the result was his breakthrough paper published in the Annalen der Physik in 1930. It’s a piece of work that is still not adequately appreciated by historians of science – and in addition to my earlier translation and annotation I will be publishing a newer version soon in the European Physical Journal – History. My analysis of Rosenfeld’s contribution and impact (or lack thereof) on quantum electrodynamics has been published in Studies in History and Philosophy of Modern Physics