brush plate material

I'm thinking it is phenolic or Bakelite.

Phenolic is known by several trade names. Common names include: Bakelite: Made from wood flour and phenolic resin, this kind of plastic is often used as an electrical insulator and in other non-conductive heat-resistant applications.

The material that makes the base of printed circuit boards is similar or the same, it just has a thin sheet of copper on one side.

Charlie

Go to the Mc Master Carr web site and look at both Garollite and hard fiber. I cannot tell from your photos which might be best.  Garolite is a linen reenforced resin material. Hard fiber is similar to fish paper and uses cotton fibers and resin. There are multiple grades of both materials. Probably get a selection of what you think will work.  Watch for machinability, some of the glass reenforced materials are impossible to work with.

look at this:  https://www.mcmaster.com/garolite-sheet-stock/

Definitely circuit board material for a modern analog. Works great as an insulator.

thanks to all

jim