Longines is a Swiss watch dating back to the mid-1800s. Longines makes quartz watches, which are battery powered, and automatic watches, which are wound automatically when worn. You only need to remove the back of the watch to replace the battery or clean the inside, something that is fairly easy to do.
Opening the Back of a Longines
Figure out what size of screwdriver from your watch kit will fit around the edge of the watch casing. You may need different-sized screwdrivers to open the cases of different styles of Longines. Take a screwdriver and carefully place it in the crevice around the edge of the watch back. If you can fit roughly 2 mm of the tip in the casing, then the screwdriver fits.
Push the screwdriver up to pop open the case. You will need to use force to open it but still be gentle in the process.
Remove the rubber O-ring or gasket. Remember to properly replace the gasket when closing the watch case. This rubber ensures that the watch is waterproof.