I need to change the battery of this watch.
Is it a screw cover? How can I open it without any special tools?
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Sign up to join this communityScrew covers have notches for the spanner wrench to grip. This cover is a snap-off press-fit cover (with a gasket inside the cover).
Any sharp edged hardened steel tool (similar to a knife-edge) can be inserted between the watch case and the cover. There will be a short "groove" in the watch case where you fit the edge to "pry" the cover off.
An easier (and better) way would be to bring the watch to a jeweller who will replace the battery for the cost of the battery alone. At the same time, the jeweller will set your watch correctly and possibly regulate it to keep time more accurately.
The watch in your picture states water resistant to 3ATM. Therefore, it has a screw back. Watches with backs that prise off are not water resistant.
Many screw-type watch backs will have notches into which you insert the arms of a spanner
To open a screw-type watch back that doesn't have notches, like the one in your picture, a professional would use a suction tool like this:
This is pressed firmly against the back to form a friction seal and twisted.
As you don't want to use a specialist tool, you need to find something that forms that firm grip against the watch back. A common trick is to use a stress ball. Hold this in one hand and the watch in the other. Press the ball hard into the back and twist.
If you don't have a stress ball, something of similar rubber consistency will do.
Don't forget that once opened, you won't be able to get the full water resistance back without specialist tools.