It is suggested that the head may have been looted from an archaeological storage area at Byblos in the 1980s during the Lebanese civil war. Mashberg has rehearsed the recent collecting history:
The owners of the bull’s head, Lynda and William Beierwaltes of Colorado, say they have clear title to the item and have sued Manhattan prosecutors for its return.
The Beierwaltes bought the head from a dealer in London in 1996 for more than $1 million and then sold it to another collector, Michael H. Steinhardt, in 2010. Mr. Steinhardt lent the relic to the Met that year, but after learning that Lebanon was disputing its provenance, he asked the Beierwaltes to take it back and compensate him.The London based dealer has not been named although other legal papers identify one of their sources (discussed by Christos Tsirogiannis, "Mapping the supply: usual suspects and identified antiquities in ‘reputable’ auction-houses in 2013." Cuadernos de Prehistoria y Arqueología 25  107-44 [esp. p. 135] ).
William G. Pearlstein, who is acting for Beierwaltes is reported to have said:
“We believe the district attorney’s position is ill-founded, ... The Beierwaltes are bona fide purchasers with clean hands. By contrast, for more than 50 years, Lebanon has failed take any action domestically or internationally to report any theft of the bull’s head.”As a point of correction, if the head was published 50 years ago, and the civil war was taking place in the 1980s, then the possible removal from the storage facility was only 30 years ago.
The Metropolitan Museum of Art is quoted:
“Upon a Met curator’s discovery that this item on loan may have been stolen from government storage during the Lebanese civil war, the museum took immediate action. We contacted the Lebanese government and the lender, we took the item off display, and we have been working with federal and state authorities, which recently involved delivering the head of the bull to the Manhattan D.A. upon its request.”I am sure that Beierwaltes will disclose the name of the London-based dealer who supplied the bull's head. From there it should be possible to identify the source of the head.