Unable to find a variant; Ambassador
As for the clamp and screw, as mentioned these are not required with the existing movement ring. Once the back is on, it will press into the ring, which will hold the movement and dial in place. Ensure that a gasket it used. Here is a photo of the clamp and screw.
Your movement uses a frictionless cannon pinion on the center pipe. There is a separate driving wheel as part of the train of wheels that has the friction cannon pinion. These wheels are very tricky to get right, not too tight and not too loose where the hands are either difficult to set or do not move when running.
In my experience, this movement is more complicated than your basic manual wind or even automatic to work on. I would get plenty of practice working on simpler movements if you are just learning. Assuming this is very similar to the 11AOAC#, there are good service manuals available.