Aviation experts said the unusual configuration of the rear rotor, the curious hub-cap like housing around it and the general shape of the bird are all clues the helicopter was highly modified to not only be quiet, but to have as small a radar signature as possible.
While the Chinese military has developed a stealth jet fighter, no stealth helicopters have been seen publicly.
In the wake of the raid and the highly-publicized mystery helicopter, the Department of Defense said it would "absolutely not" discuss the chopper, but President Obama told The Washington Post the U.S. lost a "$60 million helicopter" during the raid. While the price tag normal Blackhawks varies depending on the type, none cost more than $20 million, according to a Department of Defense procurement report.
ABC News' Nick Schifrin and Matthew Mosk and The Associated Press contributed to this report.