The crypto miners paint the video cards they used to sell them at a higher price. The technique is not naturally applied on the whole board, although it is applied only to certain areas.
According to Gomes, there are clear signs of excessive mining activity on a video card, particularly screw damage and missing labels or stickers. Other than this, users may notice a slight yellowish tinge on the memory dies and the GPU itself.
The miners conceal all of this information in an extensive use and the use of components with other video cards. The following video shows how to minimize these subtleties as much as possible.
The practice was also confirmed by the Brazilian Youtube channel TecLab, which discovered that used video cards had been marked as new by the AFOX brand. What made him suspicious was the difference in color between different GPUs from the same manufacturer.
The objective here isn't to persuade people not to acquire used video cards, but rather to avoid being scammed into paying too much for used equipment.