Will Lack of Pre-1970 Provenance Worry Antiquities Buyers?

Diorite Figure of a Priest of the Temple
of Mut (Karnak?), late 25th/early 26th
Dynasty. Privately-owned, exhibited in
the Michael C. Carlos Museum, Emory
 University, August 2008-August 2013

Nord Wennstrom discusses some upcoming sales of non pre-1970 works and asks a question: ( 'Will Lack of Pre-1970 Provenance Spook Antiquities Buyers?', November 22, 2014)

In the upcoming New York antiquities auctions at Christie’s and Sotheby’s, there are at least 90 works that lack a pre-1970 provenance, including the two highest estimated works at Christie’s December 11, 2014 sale. More than one-third of the 192 lots at Christie’s and eighteen of the 49 lots offered at Sotheby’s December 12, 2014 sale have no pre-1970 provenance.

He points out that this is difficult to explain given that it was 40 years ago that the principles of the legal trade of cultural property were defined, "how do you explain that more than one-third of the works cannot be sourced earlier than 1970?"

Are collectors willing to “roll the dice” and hope such works are legitimately out of their source countries? Should the auction houses adopt a policy that precludes the acceptance of non pre-1970 works (which would infuriate a lot of clients)?

He lists several items - let's watch what happens to them on Dec 11th and 12th.

Christie’s Lot 85. SARDINIAN MARBLE FEMALE IDOL
Christie’s Lot 91. ATTIC BLACK-FIGURED TYRRHENIAN AMPHORA
Christie’s Lot 105. GREEK BRONZE SITULA
Christie’s Lot 140. ROMAN MARBLE PORTRAIT OF ALEXANDER THE GREAT
Christie’s Lot 144. ROMAN SILVER SKYPHOS
Sotheby’s Lot 6. DIORITE FIGURE, PRIEST OF THE TEMPLE OF MUT,
Sotheby’s Lot 29. MARBLE FEMALE HEAD,