The inscription “Genuine Leather” is not a yardstick by which one can decipher a quality leather wristwatch. These are features that will help you:
Assess the stitching. Original leather watches are properly and carefully stitched.
Leather soaks up water. If neither the front leather nor back leather soaks up water, chances are that the watch is fake.
Leather can be bent easily and will show some wrinkles when bent. Fake leather is stiff.
The leather pattern will be uniformed and consistent.