Here is a Linn's article on the counterfeit Scott 4959's that Eyeonwall mentioned:
https://www.linns.com/news/second-v...graved-stampEdit to add:
I realized after posting the article link above that it dates from 2017 and there were a slew of stories in that year about newly discovered counterfeit stamps. It hammers home how long this problem has been going on and that the scale of fraud has been massive for as long. Almost ten years on before we see a comprehensive OIG report on the issue. Think of what must be billions of dollars that were lost during that time or that customers ended up paying. What should our postage rates be today if this had been addressed years ago.