This book has blurbs about how to recognize and solve, wow, many many codes. A small fraction of them: element atomic numbers, planets, Dewey and LOC and ISBN, postal codes, phone area codes, product numbers, semaphore, maritime flags, dancing men, pigpen, playfair, biphid cipher, Enigma machine, md5 hash, binary, octal, Baudot, punch cards, resistor colors, 7-segment display, music reading, circle of fifths, … Well, there are a lot.
Amongst the book's appendices are a code sheet (which you might expect) and a flow chart for recognizing coding systems (which you might not expect). An excerpt:
The next time I'm playing with a puzzling newb, I kinda want to hand them these flow charts and soon that newb will be sounding like an expert. Heck, might effectively be an expert.
There are extra bits in there that non-geocachers wouldn't use. Their ways are not our ways. E.g., GeoCachers are, most of the time, looking for numerical answers, lat/long coordinates. Apparently geocachers solve puzzles before heading out into the field, so there are systems here that you wouldn't ask someone to solve in a walking-around hunt or escaping a room—if you think you're looking at an Engima machine code in a walking-around hunt but there's no Enigma machine simulator handy, then you probably want to change your thinking. (But these tough systems would be fair game in a conference room mystery hunt, where Enigma simulators are handy.) There's a chapter about geo-things a la triangulation that are mostly of interest to geocachers. The book uses "indexing" to mean something other than what my local puzzling tradition calls "indexing". So…keep yer eyes open for gotchas, but you were gonna do that anyhow.
