The Call of Duty 1 CD Key was a simple piece of anti-piracy technology that became a core memory for a generation of PC gamers. It represented a time when your "gamer identity" was tied to a string of letters and numbers you kept in a shoebox. While frustrating at the time (especially when your little brother gave "your" key to a friend), looking back, it was part of the ritual that made the early days of online gaming feel so tangible.