First of all, in terms of appearance, Jews generally have slightly darker skin than European Caucasians, thicker eyebrows, tall noses (unlike other European and American races, the ends of the nose bridge are higher), and longer and narrower faces (even if they are obese) Or, it is difficult to change the face shape); if they cannot tell the difference, they will take out a tape measure to measure the size of the bridge of the nose (we often see the Nazis in the information film holding a ruler to measure the height of some people's noses and face size).

Moreover, Jews were adapted to circumcision at birth (you had to take off your pants for screening). Besides, this is what the Gestapo did. They had already figured out the demographic information of the Jewish settlements, etc., but they must have made mistakes sometimes!