I doubt this will be of use to many people, but here’s an idea. If you sell screws, you could use a pen, and mark down the inside of the screws’ thread. When the screw was driven, the ink would come off. That way, if the product was returned, you could tell at a glance if the stock was now second-hand, or not bought from you at all.
Look, it just says “an idea”, not “a good idea”!!
And so what if it just caught your attention because it was dated Valentines’ Day??
Expecting something else? Shame on you!