In the 1930’s two Portuguese merchants asked IWC for a large wrist watch with the accuracy of a pocket watch, and in 1939 the oversized wristwatch range that came to be known as the Portuguese (and now Portugieser) was born.  It was large due to the need to use a pocket watch movement to get the precision demanded, and the 41mm case would have seemed huge compared to the standard 30mm ish cases of the day.

Now 41mm is considered a good size for many people, and the case is not even considered thick for a chronograph.  The off white or ivory coloured dial has a retro feel to it, and the up and down chronograph layout is typical for this model.