Intaglio is a printing process that uses an etched or engraved plate; the plate is smeared with ink and wiped clean, the remaining ink in the recesses makes the print.
Intaglio is also A printing technique that produces very sharp images that cannot be easily copied without filling in.
This feature is effective primarily in document-present situations where the original document can be examined by a trained professional or scanned with a specialized 3-illumination ID scanner and analyzed with adequate forgery detection technology.
Usability in online and mobile onboarding situations is challenging as the examination is made not on the physical document but on a photograph or scanned image of it.
Ref.: https://www.gpo.gov/pdfs/customers/security_glossary.pdf