Jones in LA
··Not in LA anymore.The OP's watch appears to be a 35213000, and if so it has a press fitted case back with a hard plastic seal. A case opening ball will not be of any help to remove the back, and even if he removes it a press is required to install it again. This is a job for a professional...
Yes, I was wondering about that and just assumed it was a screw-down.
Sorry @xluxions , my approach is stymied by the caseback style. As @Archer indicated, you're going to need some help, the very least being getting the back off the watch.