That actually makes a lot of sense (the graphics card Radeon 9800) is clearly not original; it's a Quicksilver (867 mhz).  The case Model Number says M8943, which is possibly correct; and the thing blocking the modem port is actually connected (only) to the case.  

Sorry for the pics, I used a flash.

(The first shows the modem - the wire running under the board); the second shows this little metal cube; the third shows how the cube blocks the port.)