The black-bezel insert has been part of the GMT-Master mix since the reference 1675, https://www.crwhorloges.cz/best-category/baignoire/ and it was the first version to be available once the GMT-Master https://www.crwmontres.com/Collection/santos-de-cartier/ switched over to a Cerachrom insert in an https://www.iwuhren.de/produkt-Sammlungen/ingenieur/ all-gold model in 2005 (the steel version we see here came two years later).