To differentiate their mechanical offerings from the growing crowd of modernist quartz watches, IWC launched the Portofino line in 1984 as a “pocket watch for the wrist.” Designed to suggest a “marriage” watch, the Portofino features a thick, rounded case with a prominent crown, a plain dial with Roman numerals, and slim feuille hands. Although often compared to dress watches like the Patek Philippe Calatrava, the Portofino's Lepine “pocket watch” design is quite different.
The first Portofino, 1984's Ref. 5251, used a classic hand-wound movement with small seconds at 9 00 and a moon phase indicator at 3 00. In 1988, IWC introduced the Ref. 3730 and 3731 Chronograph Quartz, which used Jaeger-LeCoultre's “Mechaquartz” Cal. 631.
IWC released a classically-styled dress watch in the Portofino line in 1993, competing at last with the Calatrava. This 2-handed Ref. 2010 was just 1.85 mm thick, thanks to IWC's Cal. H/849. It lacked the rounded case and Roman numerals and used stick hands, unusual for the line, but lasted through 2005. Another departure from the traditional case style was the 1995 Ref. 3050 Romana Perpetual Calendar with its slab-sided case. Also produced through 2005, the Romana was one of the thinnest perpetual calendar watches at that time.
In 2003, IWC returned to the rounded case with the larger 38 mm Ref. 3533. Once again, however, stick hands and plain markers were used, along with central seconds. The classic Portofino dial returned in 2008 with the "Vintage" model, which literally turned the original Portofino on its side, with small seconds at 6 00 and moon phase at 12 00 thanks to the new Cal. 98800.
As IWC regained in-house movement capabilities, the complicated Portofino was revisited. In 2011, the company brought their new “8-day” Cal 59210 to the Ref. 5101. This was followed in 2017 with another tribute to the original Moon Phase model The Ref. 5251 features Cal. 59800 with 8 days of power reserve and a moon phase indicator at 12 00.