English: The verso of Francesco Fontana to the grand duke of Tuscany Ferdinando II de' Medici. (Courtesy of the Archivio di Stato di Firenze).
The picture was taken before the light restoration the letter underwent in 2009, in occasion of the exhibition "Astrum 2009: Astronomia e strumenti. Il Patrimonio storico italiano quattrocento anni dopo Galileo" (Vatican Museums, 16 October 2009 - 16 Jenuary 2010), where it was displayed.
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