Dozens of Antiquities lack dated pre-1970 provenance at Christie's and Sotheby's June 2013 sales

Nord Westrom reports, "Dozens of Antiquities lack dated pre-1970 provenance at Christie's and Sotheby's June 2013 sales":

This week, several hundred Greek, Roman, Egyptian and other antiquities will come up for sale at Christie’s and Sotheby’s in New York with many lacking a dated pre-1970 provenance – at Christies’s, that applies to the vast majority of lots on offer. More than thirty lots in the June 5, 2013 sale of antiquities at Sotheby’s in New York – approximately one-third of the 93 lots in the sale – either lack a pre-1970 provenance [...], have a provenance that consists of a previous owner’s birth and death dates [...], have a provenance that is speculative [...], or other issues that make a dated provenance difficult to establish. Meanwhile, over at Christie’s, more than 145 of 194 lots in the June 6, 2013 antiquities sale have similar issues... 

Does that 'Nilotic' silver cup look OK to you? I'd personally not put $500,000-700,000 on it without more information where it was before it 'surfaced' in 1992 and what's in the cracks, apart from silver polish.