The Silvo pickup was housed in a bakelite disc that replaced the cover plate. One solution is to incorporate a cover plate on the disc. The cover plate served only as a decoration. In use, a sample is placed between a measuring prism and a small cover plate. The bottom cover plate has the serial numbers from 1 to 150. The bottom cover plate has the serial numbers from 1 to 1857. A cover plate excludes dust and grit when the lever is returned forward. It possesses a bamboo comb like the Crossover, and a conical shaped lower cover plate.