A $500 field guide

   I was recently searching for a good field guide to add to my library (I wrote about my plight in searching for a field guide here), when I stumbled upon an interesting fact about on of my current field guides. Little did I know that he 1966 field guide that has been in my possession for four years was worth... up to $500. It's original price in 1966? $2.95. This is not a joke. And here's the clincher. I got mine for... free! I did some volunteer work in 2010 for a local library, and was rewarded by being allowed to choose four three free books to take home, and that happened to be one of the ones that I chose. I guess I made a better decision than I had thought. True, a used copy costs as little as $2, but a new version of this guide costs anywhere from $150-$500. The cheapest that I could find (new) was $94.29. My copy of this guide is practically new, so I wonder how much mine is actually worth. There is nothing wrong with it except for the fact that it is 48 years old, and it shows it (and smells; it has that classic old-book smell). Even if mine isn't worth that much, it is still an interesting find. Here is a link on Amazon to the book: https://www.amazon.com/Birds-North-America-Identification-Paperback/dp/B00C7EZ32C/ref=sr_1_59?s=books&ie=UTF8&qid=1397006000&sr=1-59&keywords=birds+of+North+America