From the CGC website Restoration Scale:
Quality Scale - C (Poor)
Material used: glue, pen, marker, white out, white paper to fill missing pieces
Piece fill obvious at arm’s length
Bad color matching, use of pen or marker. Bleed through evident
Cover cleaning resulting in washed out/speckled colors, moderate cockling and/or ripples
New staple holes created upon reinsertion, or non-comic book staples used
Trimming of any kind
Married cover/pages poorly attached with non-professional materials
Quantity Scale – (Determined primarily by extent of piece fill and color touch)
1 (Slight)
All conservation work, re-glossing, interior lightening, piece fill no more than size of two bindery chips, light color touch in small areas like spine stress, corner crease or bindery chip fill. Married cover or interior pages/wraps (if other work is present)