there is not one needed it uses a taper fit to lock that pulley onto the camshaft. works a lot like a morse taper on a machine tools like a drill press or end mill.
the timing belt is replaced with this pulley loose and not seated. then the tensioner is set, then the pulley is seated. this allows the pulley to rotate around the camshaft while setting the timing belt tension. then the cam lock is removed, and timing belt procedure continues.
no cam keyway needed.