In hindsight (I went in a different order) this bottom plate should be the first thing to remove (if you really want to take your factory radio apart which I don't recommend at all). It is just 3 screws and then you can switch to a flat head to pop it off like the picture below.
Next you can take off the back plate if you want although there is little reward for doing so, you don't really get to see much you can't already.
This is kind of a blurry picture of the S/N on the back plate I believe it's 313-2194-02
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