This article aims to give notice about the existence of a manuscript from the 17th century that copies the invective titled El tribunal de la justa venganza. This work was published against Quevedo in 1635 and its author remains hidden behind the pseudonym “Arnaldo Franco-Furt”. This new testimony, kept in the National Library of Portugal, in Lisbon, is very interesting for the critical edition of the controversial text, due to its early dating and its suitable readings in wrong passages of the princeps. The Tribunal has been always edited according to a single document, the first edition, which does not seem to have been the model for the handwritten copy. Additionally, this unknown textual source contributes to draw critical attention to one aspect that had gone unnoticed until now: the possible falsification of data concerning the place and the printer of the invective (Valencia, “Herederos of Philip Mey”), a hypothesis still needed of further inquiries.