Pierre-Louis Pierson - Léopold-Ernest MayerPortrait of a Man, c. 1855-1860. Proof on salted paper pasted on cardboard under photographers' passe partout. Dry stamp from th e studio on the montage. 18.3 x 14, cm (oval )Pierre-Louis Pierson and Léopold-Ernest MayerPortrait of a Man , c. 1955-1860. Salted paper print, mounted on cardboard and photographers' passepartout. Studio dry stamp on mount. 18.3 x 14, cm (oval)