Coulson had a tattoo of Cap’s shield on the back of his right shoulder. He’d gotten it in college. None of the Avengers had ever seen it, even Clint and Natasha; it was listed as an ‘identifying feature’ on his profile in SHIELD’s computers.
After a few months of work with Bruce and Tony creating an ink that would stay in his skin, Steve had one in the same place, of the SHIELD crest with Phil’s ID number printed below it.
Submitted by dixiechicken