An unknown black disc.

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?
   ChatGPT to the rescue?
   When Siegfried Lion asked ChatGPT to solve this problem this answer was given. Discuss!
   Note ChatGPT refers to the Cenco Gas Volume Reduction Circular Slide Rule which gives a correction factor instead of a +- difference.
2. How does this disk work?
   Note that the tick marks on the Correctie scale seem to be around the integer values, not at the values. The 5—50 scale is probably a temperature scale, in °C. The scale under the window is then the “niveau” (level) scale. Andries de Man
   
3. Can a manufacturer be identified?
   From the raw material, style and fonts used it could have been made by Swiss maker: ANOXAL. David Rance
   About Anoxal, see also Schweizer Datenschieber aus Aluminium — Schilderfabrik Hans Meierhofer AG, Mellingen.
   Anoxal stands for “Anodisch Oxidiertes Aluminium” (anodized aluminum) Andries de Man