Opening a press back--generally called snap-down or presser cases--watch case can be performed with few or no tools. Caution should be exercised when opening a press back watch case because the dust or debris can contaminate the mechanical or electronic movement. The press back watch case should not be opened unless it's absolutely necessary to perform repairs or to identify the movement. Once maintenance is performed on the case, care should be taken to press it back into place.
Inspect the case back and case of the watch with a jeweller's loupe. Locate the seam between the case back and the case. Look for a raised lip, generally at 6 or 12 o'clock on the case back. The lip indicates that the case back snaps into place. If there are screws holding the case back in place, the watch is not a press back model, but a screw-down version. If there is not a lip on the case back, it may indicate the watch is a screw-down model in which you must use the palm of you hand to rotate the case back counterclockwise to remove. Keep in mind, however, that not all press back models have a lip.
Inspect the case back to determine if it has a hinge. If so, the timepiece is a pocket watch. This means the case back will flip up but not detach from the case. Some vintage wrist watches have hinged case backs.
Insert a blunt blade or your fingernail under the raised lip and pop open the case back. If there is no lip, gently insert the blade into the seam between the case back and case. Pry open the press back case.
Remove the case back. Do not touch the movement with your fingers because the oil could contaminate the mechanical or electronic device.
Wipe down the case back and the edge of the case with a clean, lint-free cloth. Place the watch face down in the palm of your hand, or between your thumb and forefinger, once your task inside the watch is complete. Place the case back on top of the case and ensure it's aligned properly with the edge of the case. Use your thumb to press the case back into place.
Most press back cases are found on vintage watches. Although older watches have "waterproof" or "water resistant" stamped on the case back, once the press back case is removed the watch can no longer be considered completely safe from moisture.
Never force open a press back watch case if it refuses to open. You will damage the watch. Take it to a watchmaker for service. You can also devalue your watch if you scratch or chip the case.