There are four grades for slaves, and they are all different.

>U(nassigned) grade
Are mostly war captives that have not been graded yet. These women are kept away from other women until matrons can grade them.
>A-grade (highest)
Are slaves who are considered reliable enough?
These slaves are auctioned as concubines
The difference between wife and concubine should be explored another time, but unlike children of other slave grades, concubines' children are legitimate
Men have the right to promote their concubine to a proper wife
>B-grade
These are suspicious women assigned if the matron suspects a woman might try to escape
Additionally, women who are behind in their birth burden grade are graded B, however, they are typically promoted to A immediately after they are back on the schedule
B-grade women work in breeding farms, but they are given a fair bit of autonomy
These women are concealed in their own rooms, where they serve a prostitutional function
These women are allowed to pick their own customers and set their own prices
Using the money they earn, they may buy luxury goods
If B-grade slave behaves well, they might be promoted to A-grade and be auctioned off
If they attack their customers, they will be demoted C-grade slaves
>C-grade
Are the bottom of the barrel slaves, and it's virtually impossible to be promoted
These women are chained to the wall in large rooms, and dosed with heavy aphrodisiacs
Unlike B-grades, these are free to use and get fucked by the volunteers.
People who end up as C-grade are women who tried to escape or hurt someone

Children born to B or C grades are considered illegitimate, fatherless; their daughters are raised by the matrons and trained to become A-slaves.