Some like patina dials, but others don’t. In 1950s and 60s the quality of the dials were so poor and many South American people hated that the strong sunshine and humidity in their “tropical weather” made the dials of expensive watches turned to brown. That’s why Patek Philippe developed their unique enamel dials for 2526s. The quality of an enamel dial won’t change even under their severe climate, but the cost of making a beautiful enamel dials was so high. The price of a 2526 was as high as other complicated watch, such as a perpetual calendar watch, at that time. (Of course, 2526 also has the first PP automatic movement.)
In 1980s a legendary vintage watch store named “Shellman” in Tokyo, Japan had started to call 2526s as “Tropical” in Japan language. For those who don’t know the Shellman, they had sold only first quality vintage PPs, and later were the only official Philippe Dufour dealer and had sold 60 - 70% of the total 200 “Simplicity”s.
So, some wonder why this is called tropical? It’s simply a different definition in different languages.