FR2 is the brownish material that many cheap circuit boards are made of. It's a mixture of phenolic resin and paper. Apparently it's quite useful to make gears out of:

Phenolic Gears exhibits superior shear force, help reduce machinery noise, absorbs destructive vibration unlike metal gears, phenolic is non-conductive, protects the mating metal gear train, and are known to outlast metal gears under severe continuous service. (source: https://www.knowbirs.com/phenolic-gears )

(Main pic stolen from here)

(Many more pics here)

Has anyone seen these used anywhere? I've read a hint regarding pool equipment, but I have never seen them there. I assume the fibres allow them to last longer than plastic/resin only gears.