A caseback is the rear part of a watch, on the side opposite the dial. It shields the movement and other internal parts from dust, moisture and knocks. Some are solid metal, some screw off, and some have a crystal window in place of the solid cover.
How do you tell a screw-off caseback?
A screw-off back is easy to spot. Look closely at its outer edge. Notches, grooves or threads run all the way around it. Some screw backs go further and have unusually shaped edges. These can only be removed with a special wrench made to fit them. A standard tool will not open such a back.
What is an exhibition caseback?
An exhibition caseback swaps the solid cover for a window. The window is made of sapphire or mineral crystal. It lets the owner look through the back of the case at the parts inside. A clear back does not suit every watch. Watches built for extreme depth or hard use often keep a solid caseback instead.
Where it comes from
Transparent backs are not a recent idea. Makers were fitting them as early as the 1880s. They appeared mainly on salesmen’s sample watches. For much of the early 20th century, though, solid metal backs were the norm. Part of the reason was cost, since sapphire was expensive to make. It was also seen as fragile.
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