Most IWC early pocket watch movements had relatively large plates to hold the wheels. Later movements generally had relatively wide bridges (or, technically, cocks if affixed on one end only). In transition between these two design approaches, IWC produced pocket watches with long, thin bridges or cocks, which are called "finger bridge" movements.
The first IWC finger bridge movement was the Lépine Calibre 65, and its companion Savonette Calibre 66, both of which are known as “Lutetia” movements. Together these were produced in 38,740 examples between 1893 and 1930. Each had 16 jewels, beat at 18,000 half-beats per hour and was 41 mm (18 ligne) wide.
A resizing of the design in 1913 produced Calibres 73 (Lépine) and 74 (Savonette). Slightly smaller at 38 mm or 16 3/4 ligne, these also had 16 jewels but the balance was upgraded from monometallic with screws, as used in the Calibres 65 and 66, to bimetallic with screws. Reportedly, 52,500 examples of the Calibre 73 movement were made from 1913 to 1930, and another 15,000 of the Calibre 74 were produced from 1913 to 1931.
Calibre 73 and 74 pocket watches often are easily identifiable from the dial and case, without even viewing the distinctive finger bridge movement. Frequently as products of the 1920s, they often had Art Deco style dials with stylized numerals. The relatively thin cases often had striped engravings or Grecian motifs on the bezel area, sometimes filled with enamel.
Being relatively small for a full-sized pocket watch movement, the Calibre 74 was also used in IWC's first wristwatch that used a pocket watch movement, the famous Portuguese wristwatch (reference 325). 304 examples were used in the Portuguese wristwatches between 1939 and 1952.