Glossary
The rear panel of a watch case, either solid metal (often engraved with the serial number) or a sapphire window showing the movement.
The caseback frequently carries the serial and reference number, so its engraving style, font, and finish get compared against known genuine examples. A screw-down caseback that doesn't seat correctly, shows unexpected tool marks, or carries engraving of the wrong depth can indicate the case has been opened by someone other than an authorized service center, or that the caseback itself has been swapped from another watch.
Browse the full glossary, or look up a serial number in the registry.