Ferdinand was seen wiping blood from his face following the incident which took place in the aftermath of United's injury-time winning goal in their 3-2 victory at the Etihad Stadium.
After Ferdinand was struck by the missile, a Manchester City fan ran on to the pitch in the England defender's direction. He slipped and fell to the ground as he approached the player up to 10 yards away and was then obstructed by City's keeper Joe Hart, who pushed him away. The supporter was then led away from the pitch. The incident was not shown to viewers by the Sky Sports cameras.
A message on Ferdinand's official Twitter account posted at 4.34pm read:"what a result, 3points! Sweet! Whoever threw that coin, what a shot! Can't believe it was a copper 2p....could have at least been a 1 coin!"
When Ferdinand left the pitch at the end of the match he was seen to have an object in his hand which he showed to referee Martin Atkinson before he threw it to the ground.
Praising the football, the United manager, Sir Alex Ferguson, told Sky Sports: "It's just unfortunate towards the end a City fan runs on and then they throw coins at our players and that. I don't think you need that. The same thing happened at Chelsea which was masked really by all the other things that happened."
"But, you know, two fantastic teams today I think, and a fantastic game of football, and it could do without that."
The match-winner, Robin van Persie, was unaware Ferdinand had been injured as he was interviewed after the match. The Dutchman said: "I missed the thing with Rio so I will have to look back at it but that should not really happen on a football pitch."