I never saw steel braids in my life
Ralf,
Many now vintage cars had braided steel brushes, many zinc plated. Russkit, K&B, some Cox models and plenty of others had those, while others had plated or bare copper braided brushes: Classic, Monogram...
Cox for example, had two types of brushes: the early ones are braided steel with a copper wraparound sleeve to avoid separation when the assembly screw going through them was tightened. When Cox issued their later "quick-change" guide design, a new much softer braided steel with a push-on copper clip was used. Several companies copied that design, such as Cobra, but now in bare copper.
The Monogram braided brushes easily "split" at their screwed ends, because there is no sleeve to stop the braided ends from undoing themselves. Classic resolved that issue with an electric weld in the screw area. Others used... solder to stabilize that part of the contacts.