Can you please give us some sort of hint regarding which reference guide you’re referring to? I don’t think there are any particularly notable ones that we would know to look at first. I hope you just mean something like an ASCII or EBCDIC (another character encoding) lookup chart. Your statement that the guide is physical seems to suggest that we should be looking for a specific guide, but if it can also be found online (legally), then either

1) it’s really old,

2) it’s one of the few books (re)published online before its copyright expired (or maybe a periodical with free online archives or something),

3) or we need generic information that can safely be put online without breaking any copyrights.

You’re probably laughing at my wild, probably inaccurate speculation for a simple online contest in which only a few people have expressed interest and for which the prize is merely minor in-game benefits in an obscure browser-based video game that barely has any content, but instead artificially boosts the time necessary to play that content (I like long sentences (and parenthetical comments (and nested parentheses (and self-reference (come on, give us some hints))))).