Archival Methods Drop Front Box 2" 22.5 x 28.5", Gray Metal-edged drop-front boxes consist of a removable top and a bottom with a hinged "drop front" panel at the long side. Made of heavyweight Archival Grade boxboard. Metal edge clamps are corrosion treated in black polyester coating with a wax-free polyester finish on the blind side. Clamps provide rigidity and high stacking strength. The lignin content is measured by the phloroglucinol test with a Kappa number of 5 or less.