Most of Altamont's grips are made of laminated wood Micarta.
This is thin sheets of wood impregnated with a dye, then impregnated with a phenolic resin and under heat and pressure compressed into a solid mass.
These have no finish, The wood is simply buffed to a shine.
Many gun makers are using Altamont made grips because the material can be machined like metal, then only need sanding and buffing, No finish required.