On the edge of the medal: a ship's prow (used 1842-1845) and CUIVRE (copper)
The French law on the establishment of major railway lines (also known as the "Railway Charter"), passed on June 11, 1842. It defined the French railroad system, creating a model of public-private partnership.
The Latin phrase 'DANT IGNOTAS MARTI NOVASQUE MERCURIO ALAS' can be translated as: 'They give unknown wings to Mars and new wings to Mercury.' This phrase may poetically express how the new railroads will transform both warfare (Mars) and commerce/communication (Mercury).
The medal is absolutely massive at over 100mm in diameter and over 10mm thick. It weighs over 620 grams.