Not sure about your American Standard, but many shower handles have a set screw located where the handle attaches. Most likely on the side.
If this is the case, you will need either a small alan wrench or a small phillips head screwdriver, (depending on which type of screw is in it), in order to remove the screw.
If this is the case, you will need either a small alan wrench or a small phillips head screwdriver, (depending on which type of screw is in it), in order to remove the screw.