I'm kind of stumped. I'm not sure how I can remove crayon or pen marks off an old decks of cards, 40+ years old, without damaging the box itself. If it is even possible, I would definetely like some help. I have several old bike decks with marks on them. I know it is not that big of a deal, but it would be nice. Any help would be greatly appreciated.

With Crayon, you can try heating the cards over a lightbulb (not to hot or the card will warp) this should soften the wax and make it easier to scrape off.

As for pens, nothing I know of could work