The 42X is different from all the other 42s. It has a dual plunger. There is a larger, round plunger that activates first and grabs the saw blade. Inside the larger one there is a smaller one that activates next and does the setting. This makes for a more positive set with less effort.

 It has been altered. Someone has installed a flat plate that hangs down like a beard. This keeps the saw set square to the blade for a more accurate set.