Klimke Miller saddle stamps

I have a Klimke Miller Dressage saddle . The plate is worn and unreadable but the stamps on the panel are still readable.

  1. It has the KMD logo
  2. Under the logo it’s stamped art 6502 181/2
    3 to the left of the logo and at a diagonal are the numbers 842 and they are a heavier stamp.
    i know what all these indicate except for 842
    can anyone enlighten me regarding this?