Detail of 'Dollar Signs' by Arman at Sotheby's auction house in London June 8, 2015. The piece has a pre-auction estimate value of 16,000 - 22,000 pounds ($24,600 - 33,800) 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]