In my defense, I didn't lie, you do need a good quality Phillips head drivers set, but you can't forget that Casio is a Japanese brand. And being Japanese, they generally use Japanese Industrial Standards (JIS) tools, instead of SAE International that we westerners are used to. A JIS and a SAE Phillips driver will look exactly the same from a distance, but there is a very small (but important!) difference in the shape of the head:
Both are #1 Phillips head, but the one on the left is the SAE driver and the black one on the right is the JIS driver. If you look closely, you'll notice that the JIS head is a bit "shallower" then the SAE driver, but they have the same exact thickness. JIS screws have a more shallow groove on their heads, so a JIS driver will fit a little better then if you use a SAE driver.
As a general rule, Casio never overtightens their screws, so you normally can remove the JIS screw with a regular SAE driver. When you tighten the screw in place, since you should NOT over-tighten them, you can also use the SAE driver, no problems at all. However, things get tricky when you're talking about vintage or even abused models. In many cases the screws get stuck in the hole because of oxidation of the threads, and then you have to put some muscle to loosen them. And that's when it's invaluable to have a JIS set of drivers. Remember "You should use the right tool for the right job"?
I bought a set (#1, #0, #00 and #000) from Moody, a brand that I wasn't familiar with at the time but after using for around six months I can say I trust. Their tools are top notch, almost in the same league as Wiha, and like Wiha, are affordable and not hard to find on eBay. Just like with the SAE drivers, you only need the #00 and #000 drivers, so if you buy a set be sure that it has these two sizes.
If you're working on an old model, it's much safer to use a JIS driver, because the head will fit better in the screw head. Therefor, if the screw is a bit frozen, you can better apply more force with less chances of striping the head of the screw. And trust me, you DO NOT want to strip the head of one of those itsy-bitsy screws!
As I said earlier, for current/new models a regular SAE driver will work flawlessly, but if you're going to work on a watch that even has the remote possibility of the screw in question being stuck, go for a JIS driver. The headache and hassle of fixing a stripped screw is much greater then the price that you will pay for a set of JIS drivers.
By Luciano U. Werner