Tellurium
Tellurium is a chemical element with the symbol Te and atomic number 52.
Article from 2017 - In-Depth A Ulysse Nardin Tellurium Johannes Kepler, One Of The Three Original Trilogy Of Time Watches From The 1990s
"The last of the Trilogy of Time watches was the Tellurium Johannes Kepler. The Tellurium was released in 1992, and of the three it's the one that most readily combines aesthetic appeal with intuitive readability, although as with all the Trilogy watches its intended audience is an educated viewer. The word "tellurium" refers to a type of orrery – an orrery is a mechanical model of the Solar System) which focuses on the relative positions of the Sun, Moon, and Earth with respect to each other. There are several ways to implement a tellurium (the name comes from the Latin tellus, "earth") and most commonly it's done in a heliocentric version, but in the Tellurium Johannes Kepler, the Earth takes center stage."
https://www.hodinkee.com/articles/a-ulysse-nardin-tellurium-johannes-kepler-one-of-the-three-original-trilogy-of-time-watches-from-the