More details, please

All of us will acknowledge that over the centuries there have been restorers who applied their talents to work that was not completely legal. It is, however, frustrating to read in a short piece about the illegally acquired book collection of Count Guglielmo Libri (“A Count With Taste and Sticky Fingers“, by Eve M. Kahn, The New York Times, March 22, 2013) that “he hired restorers to scrub bindings and pages [of stolen books], removing telltale bookplates and stamps” without being provided with some details about this work to back the claim.