Plywood panels can have faces and backs of different grades.
In other words, the grade of panel with a BB face and a CP back would be BB/CP.
Below is a generally description of the Russian Birch 10.55-71 grade specifications.

B   Select one-piece face has a uniform appearance and is free
    from defect.  This face grade is uniformly sanded.

BB  One-piece face generally light and uniform in color.  Pin
    knots and small sound tight knots are allowed.  Occasional
    "football" patches are color matched to the veneer. 
    Sanding is smooth.

CP  One-piece face similar to grade BB in quality.  Sound knots
    and patches may be more common than BB grade.  Small open
    splits, knot holes and double patches are allowed.  May have
    some streaks and discoloration.  Sanding is smooth.

C   Open defects, all sound defects, streaks and discoloration
    allowed.  Does not have to be sanded.

Hope this helps.

Tom(tas2181)