Modern reconstructions (e.g., by the Museo della Scienza in Florence or by clockmaker Francis Maddison) have confirmed the 107 faces count from the diagrams. However, some modern replicas simplify the mechanism, reducing the number of functional hands to about 20–30 for practicality. If you are writing a historical or technical paper: The Astrarium had 107 faces (i.e., separate moving pointers).
However, that number requires careful unpacking. When most people hear "faces," they think of clock dials. Dondi’s masterpiece (completed around 1364) was not a clock in the modern sense, but a complex planetary computer. The number 107 comes from counting that displayed astronomical data. Modern reconstructions (e
Here is the detailed breakdown of that figure. Dondi’s treatise, Tractatus Astrarii , describes a brass, wheel-driven machine about 1 meter tall. It had seven distinct dial faces (one for each known planet and the Moon), plus a separate timekeeping dial. On these seven dials, there were 107 moving pointers or "faces" (Latin: vultus or facies ). However, that number requires careful unpacking
It had 7 main dials , but those dials contained a total of 107 individual hands and indicators to track the complex motions of the Moon, Mercury, Venus, Mars, Jupiter, and Saturn according to Ptolemaic astronomy. The number 107 comes from counting that displayed
This is a fascinating question because it touches on the intersection of history, engineering, and classical astronomy. The short answer is that Giovanni Dondi dell’Orologio’s .