On its release in 2000 in the limited-edition IWC Portugieser 2000, IWC's Cal. 5000 was lauded by the brand's followers. It marked the restart of completely-in-house watch movement development for the company and brought back the legendary Pellaton winding system. The movement was seen as a landmark in other ways, with 8-day power reserve, automatic winding, and a massive 16.75 ligne (38.2 mm) diameter.
In 2003, IWC introduced the Portugieser Perpetual Calendar, Ref. 5021 with a new version of the Cal. 5000. The new Cal. 50611 adds a perpetual calendar and double moon phase indicator to the movement family. The circular power reserve indicator dial at 3 00 remains, with date by pointer sharing the space. At 6 00 is a month by pointer dial, with a four-digit year window at 7 30. At 9 00 is small seconds and day by pointer. 12 00 holds a double moon phase indicator. The moon phase indicator is accurate for 577 years, while the perpetual calendar runs to the year 2499.
The fact that Cal. 5000 uses a single mainspring and barrel has impacted the reputation of this movement. As admitted by Richard Habring and other IWC staff, the watch was meant for “weekend wear” and is thus tuned to keep time accurately over a week. But the single mainspring does not deliver power consistently, so the movement runs quite fast for the first two days, more predictably for the next few, and slows down at the end. This causes issues for timing, maintenance, and daily wear. The next-generation Cal. 52000 family used double barrel construction to deliver more consistent torque and timing throughout the week.