Question: Was the one-armed man a real person?
Answer: According to an internet source, the one-armed man, Itzhak Stern, was real. Stern was a Polish Jew who worked for Oskar Schindler as an accountant and assisted in his rescue activities during the Holocaust. After the war, Stern moved to Israel.
Stern and the one-armed man are not the same person. The one-armed man, hired by Stern himself, dies during the movie, and Stern, as you wrote, survives.
Answer: No, the one-armed man is listed as "Mr. Löwenstein" and played by Polish actor Henryk Bista. He is a fictional character.
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