Glossary
The inner flange between the dial and the crystal, sometimes engraved with the serial number or a repeated brand pattern.
Rolex began engraving rehaut serials on modern models specifically to make counterfeiting harder, since replicating the fine engraved text at its exact size and position is difficult to do convincingly. An authenticator checks whether the rehaut engraving matches the model's expected font, depth, and content, and whether it agrees with the caseback serial. A blank rehaut on a model that should have one, or engraving that doesn't match, is a common tell.
Browse the full glossary, or look up a serial number in the registry.