We used to use clear glue sticks with glitter in them (aka glitter glue) to seal ports (e.g., USB), then take a picture of it. Max temp to melt glue is 190F/88

We used to use clear glue sticks with glitter in them (aka glitter glue) to seal ports (e.g., USB), then take a picture of it. Max temp to melt glue is 190F/88C, hard to remove, and the likelihood to reproduce the color flakes suspended in the glue exactly is very slim. > mix microscopic metal particles into the glue that sticks the tag to an object and then use terahertz waves to detect the unique pattern those particles form on the item's surface The concept is very similar here to the glitter glue, just way more expensive.