IWC Watch Portugieser Annual Calendar IW503501. The Portugieser Annual Calendar is available with a stainless steel case and silver plated dial. Located at 12 oclock on the dial, the annual calendar shows the month, date and day in three separate, semicircular windows. Its advance mechanism automatically takes the length of individual months into account and requires manual correction via the crown once a year at the end of February. The rare combination of an annual calendar and 7 day calibre makes this complication from IWC even more fascinating for watch connoisseurs. The arched edge sapphire glass makes the case look slimmer and underscores the watchs classic elegance. The curved strap horns ensure greater comfort even on a slimmer wrist. On the reverse side, the see through sapphire glass back provides an unimpeded view of the exquisite new IWC manufactured 52850 calibre.