The Callisto Chrono, which was manufactured in the late 1980s to early 1990s, saw a production run of approximately 25,000 units. Specifically, there's a version known as 80520N that distinguishes itself from its predecessor, the 80520. In this iteration, Breitling introduced a notable design feature by applying black paint within the engraved minute markings on the bezel, except when the bezel is crafted from gold.

What's interesting is that the Callisto Chrono also became available in a stainless steel configuration, accentuated with solid 18k yellow gold and steel rider tabs. The main hands sport a luxurious gold finish, while the smaller subdial hands may either be gold or steel, depending on the color scheme of the respective subdials.

Additionally, Breitling unveiled a special series within the 80520N family. This unique variant, bearing the label "Série spéciale" on the case-back, boasts a brushed 18k solid yellow gold bezel and a brushed stainless steel case. Notably, its dial features applied baton markers instead of painted ones, and notably lacks the numeral "12" at the top.