Revealing mistake: When Han is killed by Bruce Lee, and the door is spinning, you can see the belt that holds Han to the door.
Revealing mistake: During the fight scene between Han and Bruce Lee toward the end of the movie, Bruce Lee knocks Han to the ground. The shot changes to show a frontal view of Bruce as he lands a crushing kick on Han. It looks like Han was replaced with a dummy for this shot, as Bruce's kick seems to just send Han across the room. As I reviewed the scene, I could see that Han was actually a dummy of some sort .
Revealing mistake: In Han's first scene, when he enters the banquet hall to welcome fighters he holds both arms out and the fingers on his solid metal hand are spread. Later on after beating Williams to death he takes off his glove to reveal his metal hand. Look at the glove before he does this; he moves his fingers.
Revealing mistake: When John Saxon is shown through the dungeon by Shih Kien, a tramp looks glumly at him through the bars. This exact same shot is used later during Bruce Lee's fight with the guards.
Revealing mistake: When Bruce Lee is fighting the guards in the secret underground lair, he uses a staff to beat up the guards but there is one moment where he whacks a guard who was about 5 metres away even though the staff was only about 2 metres long.
Revealing mistake: In the dungeon fight, Lee knocks one of Han's henchmen onto the bars of the cell and the occupants grab him. It can be seen that the "metal" of the cell door is bending.
Revealing mistake: When Han's daughters/bodyguards are throwing daggers at the apples in the banquet room, one girl just blows the dagger out of her palm and catches the apple in mid air impressively. However a keen eye can see the wire attached to the dagger that pulls it from her hand (slow-mo is not necessary).
Revealing mistake: When Han kills Williams with a final blow, he slips off his glove, which reveals a metallic hand. When the camera zooms in on his hand, you can see the fingers wobble slightly. Metal will not do that. It's either his hand or some form of rubber/silicone.
Revealing mistake: When Lee's sister is seen running from the men pursuing her, she falls down and you can see the stunt mat she falls on. It looks like the makers tried to cover it up with some dirt but if you look at the lower left corner you can see the green fabric of the mattress where they missed a spot.
Revealing mistake: After the four guards have been killed by Bolo we see the body of one being dragged away by his feet, strangely the "dead" guard still has one of his arms raised and even raises it a bit higher a few seconds later.
Revealing mistake: When Han is impaled on a spear, we can briefly see he's strapped to the mirror as it turns.
Answer: Yes, he filmed all of his scenes before he died. He died on July 20, 1973 - only six days before the film debuted in Hong Kong, and only a month before the film's US debut.
TedStixon