The stationary bezel displaying the names of 41 cities around the Earth is set so that the reference city is positioned at 12 o'clock. Just inside the bezel, a disc indicating the hours in Arabic numerals rotates counterclockwise. The knowledge of the time in any of the 41 cities is direct and simultaneous.
Patek Philippe uses the Cottier patent from 1937 in the 96HU and 515HU models. The reference 1415HU appears in 1939. An exceptional 1415HU made in 1939 in platinum was sold on April 13, 2002 by Antiquorum for CHF 6.6M worth at that time US $ 4.4 million, including premium.
From 1948 Patek Philippe offers as an option for the World Time watches an enamel dial with a figure of a continental map. A very rare 1415HU with Eurasia made in 1949 is estimated $ 600K for sale by Sotheby's in New York on June 8, lot 213.
The 2523HU is released in 1953. The names of the cities have now left the stationary bezel for an adjustable ring between the bezel and the disc of the hours, allowing to easily change the time reference when traveling. Here are two results including premium by Christie's : CHF 2.7M on November 15, 2010 and CHF 2.8M on May 14, 2012.
The 2523 is too expensive and some mechanisms were left unused. Its 2523/1 evolution launched in 1957 is an attempt to simplify the assembly by changing the design of the lugs. Once more the customers do not follow and both variants are extremely rare. A 2523/1 assembled in yellow gold in 1965 and sold by the brand in 1973 was sold for CHF 1,12M including premium by Christie's on May 16, 2016.
A 2523/1 in pink gold and guilloché dial assembled in 1966 and sold by the brand in 1973 is estimated HK $ 12M for sale by Phillips in Hong Kong on May 31, lot 373.
RESULTS INCLUDING PREMIUM
Phillips : HK$ 19.5M
Sotheby's : $ 730K