Antiques dealer Raymond Scott has been cleared of stealing a rare copy of Shakespeare's First Folio.
But a Newcastle Crown Court jury found the 53-year-old from County Durham guilty of handling stolen goods and removing stolen property from the UK.
Scott, of Wingate, denied stealing the 1623 work from Durham University in 1998 and handling stolen goods.
He was remanded in custody and warned by the judge that he faced a "substantial custodial sentence".
The case related to one of the surviving copies of the 17th Century compendium of Shakespeare's plays, which went missing from a glass cabinet at the university.
It was handed in by Scott to the world-renowned Folger Shakespeare Library in Washington DC a decade later.
The trial was told Scott kept the badly-damaged volume, estimated to be worth about £1m, at his house for a decade before taking it to the Folger library where staff called police.
It was alleged he hoped to sell it at auction and share the money with friends in Cuba.
Scott was remanded in custody by Judge Richard Lowden, who told him: "There will, in due time, be an inevitable substantial custodial sentence."
The judge adjourned the case to a date to be fixed to allow a psychiatric report to be prepared.
During the trial, the jury heard experts from the US quickly suspected the book was stolen and called in the British Embassy, Durham Police and the FBI.
They discovered the artefact was an incredibly rare example of the folio, regarded as one of the most important works of literature ever printed.
It had been "damaged, brutalised and mutilated" after it was stolen, in an effort, the prosecution claimed, to hide its true origins.
Scott, of Manor Grange, Wingate, was arrested in June 2008 and claimed to have discovered the book in Cuba.
He declined to give any evidence in his defence during the three-week trial.
Durham University said it was looking forward to the folio being returned.