An EPC Kotyle from the Medici Dossier

EPC Kotyle from the Medici Dossier.
Courtesy of Christos Tsirogiannis.

Christos Tsirogiannis, Associate Professor at the University of Aarhus, has linked a photograph from the Medici Dossier with the reverse of an Early Protocorinthian kotyle that is due to be offered for auction at Christies  (New York) on October 13, 2020 (lot 27). Although only one side is shown on the Christie's online catalogue, Tsirogiannis requested an image of the reverse from the auction-house and this has confirmed that they are one and the same. I understand that the District Attorney's office in New York was informed on Friday last week. 

The kotyle is provided with a history:

• Private Collection, U.K. 
• Art Market, U.K. 
• with Peter Sharrer Ancient Art, New York. 
• Acquired by the current owner from the above, 1997.

It is currently owned by an anonymous 'distinguished private collector'.

Peter Sharrer has been linked with at least one objects that has been returned to Italy: a Roman relief that was returned from Princeton in 2002. Sharrer was also the source for objects acquired by the Fleischmans as well as the Getty, the Michael C. Carlos Museum and Princeton. He is known to have acquired items from Robin Symes.

Why are the UK dealer and private collector anonymous? Are they are unknown? And where is the mention of the anonymous European collector in Christie's history?

Will other museums and collectors who purchased directly or indirectly from Sharrer conduct due diligence on their acquisitions?