when I'm looking at a potential to buy, I'm looking for a bunch of things. Cracks in the scales, especially around the pins. rust, not necessarily bad, unless it either cuts deep into the edge, or has a pattern to it other than finger prints. An example would be rust only under the scales, or in spots that match the pattern of a tortoise colored scale. cracks in the blade are a bad sign, as are creases or bends in blade (thin blades are more prone to this) just get a general impression, see if it looks like it was actually polished, or chrome plated, or lacquered. There are good lists of brands around, but every blade is a gamble. basically, if you are unsure, don't put down more than what you'd be willing to gamble, anything could be a dud.