The Girl Who Was Death - S1-E15
Continuity mistake: When the bulldozer is on fire, the raging flames have died down completely in one shot, but are instantly burning brightly again in the next one.
The Girl Who Was Death - S1-E15
Continuity mistake: When Number 6 is trying to stop the rocket launch, the computer console in the center is emitting smoke in close-ups, but not in long shots.
The Girl Who Was Death - S1-E15
Continuity mistake: In the interior shot of Number 6 exiting the lighthouse, the red doors are open. When the shot cuts to an exterior view of him coming out, the doors are closed and he opens them again.
Chosen answer: We were never told. In the series finale [Spoiler alert] Number 6 demands an answer to that question, only to be shown his own reflection.
Jean G