According to Paul LeBrooy, in "Michelangelo's Models",
Von Praun bought this model from Alessandro Vittorio,
a former favorite student of Michelangelo. In 1562
Vittorio acquired this model from a Bologna art dealer
named Nicolo Zolfino for three Venetian skudi.
The model was latter sold or gifted to Johan Schardt who was a friend of Vittorio, When Schardt died in 1562 it ended up in the Von Praun collection as his work. In 2008, the model was reported to be in a private collection in the USA.