I have a very early one but I am missing two screws necessary to mount the device to the machine. It looks similar to the first one in Macybaby's picture, but the body of it runs side to side instead of front to back. Here is a picture and some scans from the manual (scans are from the Smithsonian Library).
[ATTACH=CONFIG]427734[/ATTACH]
[ATTACH=CONFIG]427731[/ATTACH][ATTACH=CONFIG]427732[/ATTACH]