A laser-engraved security number is not a sign of quality.
Laser-engraved tanzanites have had tiny numbers or letters engraved on their girdle (edge of the stone) as identification. Laser engraving is commonly used for diamonds, which are usually uniform in shape, cut and color, and therefore hard to tell apart. For colored stones, laser engraving is infrequent, as they are often easily distinguishable visually, and have unique combinations of dimensions, inclusions and color.
Engraving costs very little to perform at the wholesale level and is no indication of a gem’s quality. If you’d like a number or message engraved on your gemstone’s girdle, you can submit your stone to the GIA for laser engraving yourself, or contact a local lapidary to perform this task for you.