What does “Case Back” mean?

The case back is the rear cover of the watch case. It can be solid, often engraved with the brand, model, limited-edition number or other details, or an exhibition (display) back with a sapphire window that shows the movement. Case backs are typically screwed in, pressed in or held by small screws.

A solid case back protects the movement and is standard on most Rolex models, while many other brands use display backs to show off decorated movements. Dealers check that the case back is correct for the reference, that its engravings match, and that it hasn't been swapped. Tool marks or scratches around the edge can show it has been opened often or carelessly. Personal engravings on the back can reduce resale appeal, although some buyers don't mind, and a few even value a documented engraving that adds to a watch's story.

Example: 'Solid case back, no engraving, no tool marks.'