what is the left hand threaded screw called on a 1575 that holds the calender wheel

[crowncollection]

hi, This is the problem, as part of the date components of the 1575 rolex movement it has a calender wheel nut, i can get this part ref: 5093,however there is also a left hand threaded screw, does anyone know what this is called, i can not tell which screw from the diagrams i have they all look the same its to blurry ans small and none say left hand threaded screw, if someone knows the part number even better, thanks in advance .