If you're going to be taking the backs off expensive, high end watches, then you really ought to be doing it with some decent quality tools.
The Horotec screw case watch back remover tool, or case wrench, comes nicely presented in a full color box that includes a really nice little polishing cloth for when you've finished up. The wrench itself Is 7.5 inches long. It's a good size that fits comfortably in your hand and is a sturdy construction of the best Swiss quality.
The wrench comes with two studs or pegs that have tiny square tips. These need to be inserted into the wrench, making sure the curved section is facing inwards. They slot in, with a tight and firm fitting so they're not going to come lose.
Next, adjust the distance between the pegs in order to accommodate many different diameters of watches. Use the thumb screw at the back to rotate left or right to adjust it in or out. The jaws are adjustable from 18 to 65mm so you can accommodate most watch diameters with this.
On the back of the watch you're going to be working on you will notice small square indentations. These are the same size and shape as the square peg, and this is what you will use to open the watch.
1. Select two indentations which are diagonally opposite. These need to be in a straight line across the center of the watch case because the wrench will pivot around the center. Offer up the wrench but avoid actually touching the watch until you have to.
2. Use the thumb screw to adjust the pegs in or out until they match the diameter between the two indentations.
3. Place the wrench in contact with the watch back ensuring that the studs locate precisely into the matching indentations.
4. Apply light, downward pressure towards the watch and slowly rotate the wrench anti-clockwise. Ensure that you keep it parallel to the watch and rotating it around the center of the watch back.
5. Once you have loosened the back, remove the wrench and put it to one side. You can continue to unscrew the back either with your fingers or with a friction ball. This way you minimise the contact between the wrench and the watch, and therefore you minimise the risk of any scratches or marks on the watch.
To replace the back just follow the above steps but in reverse!
If this sounds like the tool for you then there is further information and a video demonstration on the product page here: