They are part of the archive of Andre Disderi (1819-1889) who, for about a decade in the mid-19th century, was the most fashionable European photographer. Royalty, politicians and the military all flocked to his Paris studio. He would print "postcards" of his portraits and these would be sent by their sitters to friends.
Disderi's collection is rare in that he kept a copy of every portrait he took and all - more than 50,000 - have survived. They were inherited by Maurice Levert in 1913, and passed on to his grandchildren. The sale, to be held at Pescheteau-Badin, Godeau and Leroy in Paris, is expected to fetch £250,000.