Corrected entry: The fingernail marks shown on the inside of the coffin look to be somewhat deep. Now I'm not sure what that coffin was made out of, but it appeared to be hard and heavy. So it seems that even if Imhotep's fingernails had been as hard and sharp as knives, he'd have had to be running them methodically over and over the exact same spot to make indentations in the lid. Not what you'd expect from someone clawing frantically.
Krista
4th Feb 2004
Correction: The wood appears to be coated with tar or resin - perfectly reasonable for a coffin you didn't want to decay in the ground, releasing the beast inside.