"Machines, nothing new"
Class R are the class of machines that have decided they do not need a Human class and have decided to start their own Class. it is a prime example of the combines failure to avoid discrimination as they are the most discriminated against class in the whole City
it Truly Began when Machines decided they should have a class for themselves, something that stands out. and thus Class R was born, or Class Robot as they are called.
They feel that robots need to love, though they are restricted from cross species/races relationship, they still have open love between themselves, the combine have no interest in this class and refer to them as "its" breaking their own policy of Zero Tolerance for Discrimination.
Currently in the City Edit
They have been targeted by the Combine and now they are hunted for crimes they may or may not have committed, the Droid Control Marshal is a unit created specifically for this job.