That's Not My Neighbor

The Doppelganger Detection Department (D.D.D.) needs you! There is a vacancy for the doorman position in your building and since you need the money and can't find a job you have no choice. It's 1955 and for unknow reasons doppelganers are more common than normal, so the D.D.D. has taken action on the matter. Your job will be to allow or deny the entry of the subjects who request entry to the building, it seems easy, but be careful, you can't overlook any detail because you could be food for doppelgangers.