a few examples:
a really poor fuzzy image of a Parker 51 with "watermelon" two tone gold cap. Kind of looked like that, no bids, low bids I got it for a modest amount.
Poor image and no description other than "vintage Wahl fountain pen"... oversize hard rubber woodgrain, the color was NOT red/black, it was more a mix of amber and brownish, maybe faded, who knows. Got it, turns out to be a prototype HR in a magnificent swirl. Had a few fanatical Wahl collectors chasing me at pen shows after that...I finally let one of them catch up to me
Box of miscellaneous pen related paper ephemera, newspaper ads, ink blotters, etc. A corner of one piece of paper was peeking out, it was a complete hard cover early 1900's Waterman catalog, full color with gold foil printing for gold filigree images. Bought for a very modest amount, the catalog is considered very rare and sells for quite a premium.
so once in a while there are gems to be found simply because the sellers have no idea what they have. But the rule is "always know what you are looking at."