I believe it is best to leave this to the watchmaker. Tightening a case-back and ensuring the watch leaves up to the specified depth needs more than screwing it back on. Seals and testings is a must. If you do not dive then you can tightened it back...
For me it's a triple A. A1 for style (with a real bronze case with a great patina effect, bronze buckle and bronze keepers) A2 for build quality (including known reliable movement) A3 being I'm sensitive to it, it's Italian and moreover made by...
Most importantly is you, me and many others like this watch. Of course it is not for everyone, nonetheless it is a great real pro-diving watch. For now congratulations to you and I wish you plenty good times with it.