Thanks for finding/posting that... I've heard the term "celluloid" many times, but never really had a grasp of what the material was. It must date all the way back to the turn of the century... right?
BTW, Erik kindly and promptly issued me a full refund as soon as I expressed my concerns. Very courteous and effortless. He provided some pretty decent rationale for the Pin being authentic, but I would not have felt completely comfortable with it, based on the feedback here (and in another forum).
It may just be one of those items that forever remains a mystery.