+1 on fuzztone’s formula. I also use the ad as an indicator. Does the seller offer specific details that accurately describe the product, AND do the photos confirm the description. For instance, if an amp is rated 9, but you see dings or scratches in the photo, beware, or ask the seller some direct questions. (Not every seller responds well to this approach, which may also be useful information.) The good news is that honest, trustworthy sellers of surplus audio goods far outnumber those who may be somewhat deceptive.
