M6 loose brightline selector - how to fix?

[menos]

My M6 has some play in the lever for selecting the brightlines.
The machinist in my blood wants to fix this - how do I get into it?

There is a top cap on the levers mounting axle with a small hole in the lever at 1200.
Is this for levering the cap off?

 

[Ken Ford]

The cap button is threaded - you need either a very small strap wrench or a proper ring wrench.