Knowing What One is Buying: Christie's Gapped Collection Histories

David Gill ('Robin Symes and lots at Christie's', Wednesday, December 10, 2014) discusses the collecting histories of two of the items which turn out to be included in the so-called Schinoussa Archive (linked to Robin Symes). As he says:

Authenticated and therefore reliable collecting histories are important. Auction catalogues need to be able to demonstrate the previous owners of a lot. After all, potential buyers need to understand what they are buying.

So why is it that neither the stated history of Lot 51 (Egyptian alabaster vessel) nor that of Lot 139 (a chunk of marble building) have any mention of the dealer concerned? Is a collecting history:

(a) "a decorative listing of a few people you might have heard of who've had this", or
(b) "verified history of the passage of this object onto the licit antiquities market leaving no place for monkey business"?

Gill notes the appearance of an "[anonymous] private collector 1992" in the collecting history of one of the objects, and asks whether that is Symes. Perhaps we could ask the dealer who the object was "with" at some unknown (undisclosed?) date before it passed to the final owner mentioned in the list. What use is a collecting history with gaps for establishing legitimate passage and where were these objects prior to '1980' and 1987 respectively?

UPDATE 11th December 2011
The two lots concerned here were withdrawn by this morning.