Display caseback

A display caseback has a transparent window, usually sapphire, that shows the movement from the back of the watch.

It lets a buyer see the movement's finishing and confirm what's inside, which can help sales. For you, it's a quick way to check that the movement looks correct for the reference.

Look through it at intake for dust, loose parts, or a movement that doesn't match the expected caliber.

Some references were offered with both solid and display backs, and a display back fitted where the reference should have a solid one is a modification worth noting. Scratches on the display crystal itself are usually cosmetic but visible to buyers.

Using it when you sell

A good photograph through the display back shows the buyer the movement and answers questions before they're asked. Take it in even light without reflections; the guide to photographing a watch for sale covers the setup.

If a display back has been fitted to a watch that came with a solid one, say so. Beyond originality, a swapped back can change the water resistance the watch was rated for, which matters to a buyer who swims with it.