In 1836 Collas developed a new machine that carefully copied, in mathematically precise reduction or enlargement, the relief and chiaroscuro of medallions and other bas-relief objects onto engraved steel plates, producing what he called a ‘numismatic engraving’ also known as Anaglyptograph. The collection of the Trésor de Numismatique, a precursor to photomechanical reproduction, contains over a thousand engraved plates and reproduces upward of 15,000 specimens. Brunet V, 938 (International Weekly Miscellany, No. 9, Vol.1, p. 257, August 26, 1850)
Benson, Richard, and David Frankel. The Printed Picture. New York, NY: The Museum of Modern Art, 2008. p. 93. (alt)
Hanson, David A. Checklist of Photomechanical Processes and Printing, 1825-1910. , 2017. p. 35 (alt).
Paris, Muséum national d’Histoire naturelle (MNHN), bibliothèque centrale