One of the returns from the J. Paul Getty Museum to Italy was an Etruscan duck askos (discussed by Gill and Chippindale in IJCP 2007 [abstract]). The duck was a gift of Vasek Polak. The identification was provided by a polaroid seized in Geneva.
Felch and Frammolino in Chasing Aphrodite have discussed the "donation" scheme of objects that passed through the Summa Gallery. They note (p. 36) that Polak donated $761,000 worth of antiquities. There are 292 records listed on the Getty database, although there is a distinct lack of information about their sources.
What was the origin of the Etruscan ivory fragments donated in 1982? What about the fragments of Athenian pottery given in 1981? The list could go on.
Has the moment come for the Getty to release the complete collecting histories of such "donations"?