Revealing mistake: On the raft, when Number 6 starts to take apart his radio, you can see that the raft is in very shallow water but it's supposed to be out at sea. (00:10:25)
Revealing mistake: When Number 6 is fighting the two smugglers on the deck of the boat you can see creases in what is supposed to be a foggy background.
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