Detail of 'Dollar Signs' by Andy Warhol is seen at Sotheby's auction house in London June 8, 2015. The piece has a pre-auction estimate value of 4.5-6.5 million pounds ($6.93-10 million) and forms part of a private collection of twenty one works inspired by the US dollar which will be auctioned in London on July 1 and 2. [Photo/Agencies]