The Stone Aztec Calendar coin from the Archeology and Symbolism series is of exceptional collector value. Struck from 3 ounces of 999 silver and with a diameter of 65 mm, it was additionally plated with 24-carat gold. The high relief adds a unique three-dimensional feel and detail to this coin, highlighting both its artistic design and historical significance. The Aztec calendar stone is a late post-classic Mexica sculpture housed in the National Anthropology Museum in Mexico City, and is perhaps the most famous work of Aztec sculpture. The stone is 358 centimetres (141 in) in diameter and 98 centimetres (39 in) thick, and it weighs about 24 short tons (21.4 long tons; 21.8 t). Shortly after the Spanish conquest, the monolithic sculpture was buried in the Zacalo, the main square of Mexico City. It was rediscovered on December 17, 1790 during repairs on the Mexico City Cathedral. Following its rediscovery, the calendar stone was mounted on an exterior wall of the Cathedral, where it remained until 1885. Most scholars think that the stone was carved some time between 1502 and 1521, though some believe that it is several decades older than that.