I just did some research.
Cellidor is tradename for Cellulose Acetate Butyrate. An amorphous, transparent thermoplastic that is NOT polymerized as most plastics are.
I take it amorphous means "not crystal", which is probably what gives rise to cellidor's impact resistance. Has very low polar solvent absorption, making it highly weather resistant, but being a cellulose ester modified by acids, it is easily attacked by organic solvents.
I remember 20 or so years ago, my dad got brake fluid or cleaner on the handle of his SAK, and it caused the cellidor to swell up and get all "mushy".
Whereas most plastics are monomers strung together into polymers, Cellidor is chemical modification of cellulose, which is already in a form of polymer in nature.
Interestingly, it is clear in color, and is used alot in plastic blister packaging and UV goggle lens (Cellidor is a.k.a. UVEX). I guess that explains how they have the transparent scales. Impact resistant tool handles are usually made of Cellidor (or Cellulose Acetate Butyrate).