To be fair, it sounds like insider based "embezzlement" right? Someone signed off on the scrap metal samples and didn't bother to have any testing of future deliveries? Or perhaps had someone sign off on future deliveries without checking their base metal content? Either way, insiders exploiting weak internal controls to personally profit is certainly one of the more common "thefts" mode, whether its employees taking things home from the store or accounts writing checks to their cousins against fake invoices.

I often wonder if there is a correlation between companies with higher pay inequity and this sort of theft. One leg of the fraud triangle is because the fraudster has a sense that they "deserve it" after all.