The unnoticed suppression of José Pérez Hervás’ entry from the historical body of Enciclopedia Universal Ilustrada Europeo-Americana (1905-1934) leads the authors to analyze important aspects of the history of this popular encyclopedia. The relationship between Pérez Hervás and Espasa is dissected by using news media hemerotecas, Pérez Hervás’ book Espakalpe and the Circular published by the Centro Enciclopédico de Cultura. Cataloging problems in libraries were detected as a consequence of intermingling first edition volumes with other prints published after the civil war in Spain. The total number of modifications at the present time is impossible to quantify although this investigation advances a few. Important alterations, which contradict the encyclopedia’s policy, force us to vindicate JPH’s contribution to the encyclopedia as well as to claim that all previous works about the encyclopedia must be reevaluated as a result of these new findings.