Christie's and Sotheby's jump-started the fall season last week with announcements of respective blockbuster consignments including a $100 million Modigliani nude and the roughly $500 million collection of illustrious former Sotheby's chairman A. Alfred Taubman's estate.

According to the 8-K SEC filing Sotheby's made on September 9, the publicly traded auction house is betting big on the $500 million Taubman collection, having given estate overseer and Taubman's son Robert a financial guarantee "for the collection at approximately that level." The SEC Filing was first flagged by the Art Market Monitor's Marion Maneker in a post this morning.