The letters in Patek Philippe reference numbers and movement codes are abbreviations of French words.
| Letter | French Word | English Translation | Case Material |
|---|---|---|---|
| J | Jaune | Yellow | Yellow Gold |
| G | Gris | Gray | White Gold |
| R | Rose | Pink | Pink Gold |
| A | Acier | Steel | Stainless Steel |
| P | Platine | Platinum | Platinum |
| T | Titane | Titanium | Titanium |
