The meaning of the chronometer is vague and it usually refers to the timepieces that have been officially certified by various official testing institutions, achieving the strict standard of accuracy of chronometer. It doesn’t have direct relations to the Observatory. The word of chronometer comes from the ancient Greek language, which means the timepiece originally. It has a specific meaning that is the watches with high precision when the human beings invented the watches. For a long period, the Chronometer specifically represents the accurate boat watches and pocket watches with bascule escapement.
In 1925, Swiss Association for Chronometry has defined Chronometer as the timepieces which have successfully passed the testes from the institution while in 1973, Switzerland established the Contrôle Officiel Suisse des Chronomètres（COSC). The standards of the Chronometer was made by COSC. The watches broadly defined as chronometer are numerous but they are not the real ones that have been certified by Observatory. The precious Rolex fake with yellow gold case could be regarded as such a real Observatory Chronometer.
Girard-Perregaux 32A gold watch and Seiko 45GS Astronomical Observatory Chronometer are both the real Observatory Chronometers too. Observatory Chronometer has usually been created especially for competition, and few models will be sold to public. The Rolex knockoff with black leather strap was released with a limit amount of only 24 pieces, making it really precious.