Sotheby's New York and the Swiss photographic archives

The link between material derived from Giacomo Medici and Sotheby's in London is well documented through Peter Watson's Sotheby's: Inside Story. But what was happening at Sotheby's in New York?

Let us take three recent identifications made from Swiss photographic archives:

a. Paestan krater: Sotheby's NY June, 23 1989, lot 196.
b. Peucetian clay stamnos: Sotheby's NY 1995.
c. Apulian rhyton: Sotheby's NY June 8, 1994, lot 189.

Who consigned these pieces to Sotheby's? Did the same person or persons consign other material?