Adjustment on Breuer Tonearm

Does anyone know what adjustment knob beneath antiskating knob(on top) is used for?
Instructtion (sheet of paper) doesn´t seem to say.
I can´t find it anyway.

Gladly appreciated & Many Thanks!
The adjustment knob on the side of the arm is for dynamic tracking adjustment. You can set the counterweight and then add more VTF with that knob up to aprox. 1.1 grams. Gently turn the knob counter clockwise to add more dynamic tracking force.
On the Breuers I've owned I found the Static balance to give a purer sound but your version may vary.

I.E You level the arm /cart out to equal balance sliding the counterweight--leaving the Knob mentioned in Zero position--then turn the counterweight to set the VTF.
A precision stylus gauge is used to determine the VTF.

Superb arm- good Listening,

Many thanks Pcosta (helped me again).
BTW got my Mint Protractor a while ago and now I finally think I´ve reached sweet spot (or very close). Noticed that cartridge front doesn´t necessarily have to be parallel
with headshell for best result. Could be that needle is not perfectly aligned at assembly ad maybe that needle is displaced after usage. But the sound is terrific with huge soundstage. I´ve just added Adapt Response AR6 conditioner on front end. Once you get the phase right of all PC:s soundstage opens up even more with better detail and more natural sound.
I was very sceptical about conditioners before.
Happy listening!