Seiko watches can be difficult to open. They usually have two types of backs. The first type snaps on and only requires a screwdriver to open. The second screws on and requires specialised tools. These tools are available for purchase to the general public, but they are also kept on hand by most jewellers and Seiko dealers, who are usually happy to open your watch free of charge. If you have the tools, however, these types of backs are fairly easy to open, but sometimes they require a little muscle to loosen.
Remove the watchband if it's in the way. Use the smallest-sized mini screwdriver to either pop out the spring pins or unscrew the screws that hold the watchband in place.
Turn the watch over. Locate a notch along the outer edge of the watch.
Select the flathead mini screwdriver size that corresponds with the size of the notch. Insert the head under the notch and gently pry off the watch back.
Remove the watchband if necessary. Refer to Step 1 above.
Place the watch case face down in the case holder and tighten until the holder has a firm grip on the watch.
Adjust the case wrench until it fits the notches that are spaced evenly around the edge of the watch back. Fit the wrench into the grooves and twist counter-clockwise to loosen the back. Finish unscrewing it with your fingers and lift the back off.
Most jewellery shops or department store watch counters will open your watch and change the battery for you for no extra charge beyond the cost of the battery. Check with the store where you bought your watch to see if they handle minor repairs and battery changes. If so, letting them handle it will increase your chances of getting the watch replaced if something goes wrong.
Opening the back of a Seiko watch yourself can resulting in voiding the watch's warranty or in destroying the seal on waterproof and water resistant watches. When in doubt, it's best to let a professional handle it. It's often easier to get the back off of a Seiko than it is to put it back on. Don't lay the watch on a hard surface while exerting pressure on the back. This is a good way to crack the crystal, and yet another reason to leave it to the pros.