Cleveland Museum of Art: "convincing evidence of wrongdoing"

Steven Litt has been covering the story surrounding the return of antiquities from the Cleveland Museum of Art ("Cleveland Museum of Art will return tainted antiquities to Italy Wednesday", The Plain Dealer April 22, 2009). Today's return has been played down by the Museum: there is no press release relating to the return.

Timothy Rub, the museum's director, was quoted by Litt,

"I look upon this as a kind of mechanical thing ... The big news for me was the signing of the agreement."

Litt concludes his report with this:

Rub said the lesson of the negotiations with Italy is that the museum will return objects to foreign countries only in the face of convincing evidence of wrongdoing.

Does this imply that the management team at the Cleveland Museum of Art has accepted that the objects returned to Italy were acquired against a background of "convincing evidence of wrongdoing"?

If that is the case the museum - and Rub in particular - has a responsibility to disclose the collecting histories of the returning pieces.

Litt has earlier suggested that (according to Italian sources) the objects had been acquired from Fritz Bürki, Robert Hecht, Giacomo Medici, and Robin Symes. Is this correct? Do any other pieces in the collection come from the same sources?