L&N low-thermal-emf switch cleaning

[TimFox]

I have three of these beautiful, classic, Leeds & Northrup switches.
They seem to use hardware similar to the "low-thermal-emf binding posts" from L&N used in my Keithley 260 Nanovolt Source.
The body is real bakelite, and the metal is some kind of copper, not plated, possibly Be-Cu (?).
They are are a bit old, but in good condition.
What cleaning product and technique are recommended for the switch metal parts?
I don't want to use an abrasive, but I also want to ensure the surfaces are free from copper oxide, which has a high emf against copper.
The photo was taken above a 0.5" grid.

[MK]

The contacts will be pure copper, use brasso or similar to remove the oxide, and then ipa or similar to remove the last traces of the brasso.

[WattsThat]

Bon-Ami powder available in the cleaning materials isles should remove the oxides without scratching the base metal, it’s straight feldspar without any abrasives added as you might find in other scouring powders.

I’d just rinse well with di or distilled water.

[Conrad Hoffman]

They must travel in threes, as I also have three. A couple are missing the knobs. They're excellent switches and I've used them for winding resistance/temperature measurements. It took my coworkers a bit of time to get over the size!