Case first, movement first

Cartier's watches are designs: the Tank of 1917, the Ballon Bleu of 2007, the Santos, each a case shape first and a movement second, and the Ballon Bleu alone is 51 of the 188 Cartier watches here. IWC's watches are movements in cases built for a job: the Pellaton winding system, the seven-day reserve of the Portugieser and Big Pilot, the soft-iron cage of the Ingenieur and the Pilot's Watch, a median case of 42 mm and 14.3 mm thick.

Movements

Both bought ETA's 2892 for decades, and the library still shows it: Cartier's 049 and IWC's 30110 are the same base, which the 2892 piece describes. Cartier's in-house era began with the 1904-PS MC of 2010, its most common movement here; IWC's runs from the 1950s Pellaton calibers to the 52010 and the 69000 chronographs, and the Pellaton piece explains what makes them IWC's own. Cartier's 188 watches run on 22 calibers, IWC's 1,763 on 135; 27 per cent of Cartiers are hand-wound, the Tank Louis Cartier among them, against 11 per cent of IWCs.

Complications and materials

IWC is the more complicated brand in this library: 27 per cent of its watches are chronographs and 9 per cent perpetual calendars, most of them Kurt Klaus's from the Da Vinci. Cartier's complications sit in the Rotonde de Cartier, the mystery hours and flying tourbillons, at 5 per cent tourbillons and 8 per cent chronographs. Cartier is 57 per cent precious metal and 28 per cent steel; IWC 42 and 47. Water resistance is a dress rating at both, a median of 30 m at Cartier and 50 m at IWC, with the Aquatimer and the Calibre de Cartier Diver the exceptions.

30 per cent of the IWC watches here are limited editions and 7 per cent of Cartiers; the rarity medians are 5 at IWC and 4 at Cartier.

The pairs

The Tank and the Portofino are the dress watches, the Ballon Bleu and the Portugieser the round everyday watches with a manufacture movement, and the Calibre de Cartier Diver and the Aquatimer the two 300 m divers. The Rotonde and the Da Vinci hold the complications.