This is a highly rare 1940s Girard-Perregaux "Large Date" Art Deco Step Design Rectangular Silver Roman Dial watch.
The valuable 1st original Large Date, which is still being produced today, is equipped with the tonneau-shaped Cal. 97 movement. It features a unique large date mechanism that separately displays the tens and ones digits of the date. Unlike modern date mechanisms that automatically transition from the 31st to the 1st, this watch requires manual adjustment using a button coaxially positioned with the crown, allowing the date to be set up to 39 days.
While this system may be somewhat inconvenient for a calendar watch, its distinctive mechanism and Art Deco design continue to fascinate vintage collectors. This piece is an exceptionally rare treasure, not only due to the rarity of the model itself but also because of its excellent preservation, further enhancing its value.