I have overhauled about 3 alternators and they all had only 2 brushes. So 164 alternator can't be so unusual. I think those extra brushes would go in to the regulator once it's brushes wear off.
You might have to de-solder and remove the worn out brushes and re-solder the new ones in.
Sent from my SM-J730F using Tapatalk
That makes sense. Thanks.