I found a two tone brush grey upper and an aged orangey yellow base does this qualify and is there someone here who could restore it if I get it at a reasonable price?
Old bakelite or catalin resin brushes that have aged to a nice butterscotch color qualify as a butterscotch brush. These resins started their life as usually an off white then age to butterscotch. Some old bakelite brushes started their life as various colors (reds, greens, others) then changed over time to deeper or different colors and while technically not butterscotch they are still quite desirable.
The brush you mention may or may not be a butterscotch...a picture would help. If it is in good shape it sounds like a winner for a restore.
Rudy Vey is your man for the restoration should you not want to take on the task by yourself (it is quite easy).
Is there any way to facilitate "buterscotching" in a old brush that hasn't yet ripened? Is it exposure to UV that makes it change? Heat? I want a VERY buttery butterscotch handle to restore, but the ones I find on ebay aren't the right colour yet!
An easy way to tell bakelite from just regular plastics is to give it a good rub. Rub it enough to heat up the plastic, and then give it a sniff. Bakelite typically gives off a smell similar to burnt hair.