At 33:48 into Part 1, there is a shot of the actor playing Hitler drinking tea, with his pinky raised delicately. Then at 51:58 there is an archival shot of Hitler himself drinking tea - with his pinky raised just as in the previous shot.
The archival footage of Hitler is from Leni Riefenstahl's 1935 propaganda film of Hitler entitled Triumph des Willens (Triumph of the will.)