Improved stone-carving techniques lead to extraordinary detail on Costa Rican effigy metates (grinding tables). Complex human, animal, and composite beings, often part of multifigure scenes, embellish the stone tables. The metates go out of favor by about 900 A.D. ca. 600 Machine-tools for working stone, ceramics, concrete, asbestos-cement or like mineral materials or for cold working glass, (other than sawing, grinding or polishing machines) 2019 Costa Rica 12.45 Japan Export 846490 United Rentals offers walk-behind scarifiers with optional vacuum attachments to help you with the clean up. Because scarifiers use these wheels, they leave the surfaces a rough texture. A concrete grinder would be able to smooth this roughness and prepare the concrete for coating. Cat Class Code. 220-5150.