Abstract: A seal assembly which is screw threaded onto the stem of a wrist watch with the seal and stem being related to a tube connected with the watch case in a conventional manner. The screw-on seal of this invention includes an internally threaded member engaged with an externally threaded portion of the watch stem with the exterior surface of the internally threaded member being provided with a groove or notches receiving an O-ring seal to enable relatively quick and easy repair of a watch when an existing stem is broken due to weakened areas in the stem formed when a conventional seal is positioned in a groove on the stem. This seal assembly can also be used in new watch construction especially when installed in combination with a conventional water seal crown thereby providing double protection against entry of water, moisture, dust and similar material that may adversely affect the operation of the watch.