About the Employer Class field
An employer is assigned their Class by Perform Zone automatically.
Client = have made a placement with the employer before
Customer = have taken a job on but have not filled it.
Prospect = never taken a job on.
The employer Class field is used as one of the nine qualifiers in the Job Qualifier ratings calculations. The theory is that the more placements you have made with the employer, the more likely you will make another.