Slide rule workshop

Leo's mystery slide rule Nr. 2

F An unknown black disc.

Click images for magnification

Data:

  • Diameter: 98mm
  • Material: Aluminum
  • Front has 1 rotating disc with division from 5 to 50 and a fixed disc with a division from minus 20 to plus 25.
  • A third scale is visible through a small opening with a division from 30 to 150
  • Text on front indicates “correction” , “level” and “25°C”
  • In the middle is a name that is not easily readable and only “C ??BIJ” can be deciphered
    “C ??BIJ” is probably “CORR. BIJ”, indicating "Correction at 25°C" Andries de Man
  • Back side no information or divisions.

Questions:

  1. What is this disk for?
  2. How does this disk work?
  3. Can a manufacturer be identified?