"Limited-edition pencils that feature a non-photo blue core that disappears in scans and photocopies. Blue and natural two-toned barrel, silver ferrule, silver clip, white eraser, and white imprint." - Blackwing website
Only 2500 sets were made. These are great for sketching, then going over with pen, ink, or another pencil, then scan or photocopy and those blue marks should be gone!