The discovery of galley proofs that were printed in 1938, but not published, includes translations of classic scientific texts-Newton’s Principia and Leibniz’s Dynamica - as well as a source book on the history of physics compiled by the renowned Soviet historian of science, Boris M. Hessen. The preparation and intended publication of these books reflects the sharply rising interest in the history of science that existed in the Soviet Union during the 1930s. Over an extended period of time, Soviet publishing houses had been issuing a special series on “Classics of Science” edited by S. I. Vavilov and B. M. Hessen. The works of Galileo, Kepler, Newton, and Leibniz presented particular difficulties for this project, since they employed outdated mathematical techniques and notation systems unknown to modern readers. For example, the existing Russian version of Principia by A. N. Krylov, despite its extraordinarily useful mathematical commentary, for the most part offered a strongly modernized translation of Newton’s original. A Russian translation of Dynamica-Leibniz’s major contribution to physics-did not exist at all. This essay discusses the history of efforts to translate these works of Newton and Lebiniz, analyzes the quality of the translations, and also tries to determine the identity of the translators. Although the books were already typeset, proofread, and double-checked, they did not see the light of day, as in 1938, the plates were dismantled. A similar fate befell Hessen’s source book on the history of physics. The arrests of persons involved in the project - S. Ye. Arshon and B. M. Hessen, who both died during the terror-most likely led to the ban on publication. To this day, Russian readers have not had at their disposal Russian translations of these classic texts.