This striking set of semi-postal stamps from the Netherlands features modern geometric and optical designs created through intricate line patterns and mathematical forms. Issued to support charitable causes, each stamp displays abstract shapes such as cubes, concentric circles, and layered grids, highlighting the minimalist graphic style popular in Dutch design. The denominations include surtaxes (e.g., 12+8c, 25+10c), indicating their welfare contribution. These visually captivating stamps are attractive to collectors interested in design, geometry, and modern art themes in philately.