It was Buddy Ruyan's defense on the 1985 Bears. As far as I know no one uses it in a pure form any more. The Titans ran it part of the time in the recent past. It went out of favor in the early 1990s as the cover 2 became the fad.
ally it is very aggressive defense with only one safety playing back. I am not sure how it would work with all the talent at the WR position and the coverage rules, but I think you would need one great cover corner to make it work. I guess Baltimore figures they have that in Neon Dion. Alexander probably is not fast enough to man cover a speed receiver the whole game.