You can find out more at
www.orionbluebook.com.
From their website:
"How did the Blue Books begin?
In 1973, Roger Rohrs, owned a chain of retail stereo stores along the California coast. Being unable to be in more than one store at a time, he was losing money if an inexperienced salesperson took a trade at too high of a price. Many times the salesperson would listen to the consumer who claimed what the product would be worth since he remembered what he had paid. The was also a problem with store's credibility if a customer brought the product in for evaluation on two separate occasions and was helped by different salespeople who each quoted a different price. To eliminate this problem, Mr. Rohrs wrote the original Orion Trade-In Guide. Not only did it eliminate costly trades, it worked as a training manual for new salespeople."
So it obviously began as a profit margin tool for a retailer, i.e., not to be trusted by Joe Consumer (works for the seller, not the buyer). Many guides like this have been written over the years, most of them entirely inaccurate as to market value, but rather reflecting what the retailer would hope to receive if an uneducated customer walked through the door. The highest end of musical instruments belongs to the string world, and at the higher end of that valuations are based on market history, rather than pie-in-the-sky prices. Instruments by a particular maker have received prices of (x) in previous auctions; a particular instrument is either a better or poorer example of that maker's work; that particular maker may or may not be in favor at the moment; where the instrument was made is important; the condition of the instrument is also obviously a factor. Honest businesspeople realize that many factors affect the value of anything, and hopefully don't use this Orion Blue Book as a guide.