Léon Bottou's 2017 foreword states the reissued Perceptrons text is the 1969 first edition (fourteen chapters, 0–13); the Prologue and Epilogue were written for the 1988 Expanded Edition

Léon Bottou's foreword to the 2017 MIT Press reissue of Perceptrons states the book's compositional structure directly: "This reissue contains the first edition text of Perceptrons, with fourteen chapters numbered 0 to 13. The accompanying Prologue and Epilogue were written for the 1988 expanded edition." The 1969 content is therefore the fourteen numbered chapters; the Prologue ("The View from 1988") and the Epilogue are 1988 additions.

This matters as an independent line of evidence for the vault's credit-assignment thread. The claim that "credit-assignment" belongs to the 1988-added material rather than the 1969 body (claim-perceptrons-credit-assignment-only-in-1988-epilogue) had rested on page-count triangulation — 292 printed pages in the Expanded Edition versus 258 in the 1969 first edition, with the phrase indexing in the Epilogue region. Bottou supplies the same structural fact by statement rather than inference: the 1969 and 1988 layers of the single 1988-printed book are separable, and the Prologue/Epilogue sit outside the 1969 text. It is a named-academic source (Tier 2) writing for the official reissue, describing the book's own construction.

The corroboration is structural, not textual: the foreword is only Bottou's nine pages, not the book body, so it cannot itself be searched for the phrase "credit-assignment." It establishes where the 1969 boundary falls, which is the mechanism by which the phrase can be 1988-only even though it appears in the single available scan. The residual gap — a direct read of the 1969 body itself — remains at question-verify-perceptrons-1969-credit-assignment-absent, and is compounded by the fact that no standalone 1969 scan is freely available (claim-perceptrons-1969-standalone-scan-not-freely-available).