Screw back is the caseback of a watch that is attached by screwing it into the watch case, affording an impenetrable seal. The design closes the gaps in the watch in such a manner that no moistures or debris may enter the movement. This would protect the delicate workings of the piece. Screw backs are usually made of the same material as the case of the watch, making them an seamless fit. Mostly, in high-end and luxury watches durability as well as reliability is a crucial factor.
The screw back mechanism requires a special tool for opening. Thus, there is an added benefit in terms of safety against unauthorized access into the watch's mechanisms. It's not just securing the internal mechanisms but also adds to the overall aesthetic of the watch because the design of the case remains sleek and unbroken.
