If you are repairing legacy German equipment (e.g., Bosch, Mannesmann, or Demag machinery from the 1980s–1990s), the original drawings will often call out "DIN 1624 St 35 Si." Without the PDF, you cannot confirm the original hardness or tolerance.
It defined chemical composition, mechanical properties (tensile strength, yield point, elongation), and permissible tolerances for dimensions and shape. din 1624 standard pdf