Digital scan of a 35mm slide. Black-and-white comparison of four models of Starr-Edwards heart valves labeled (clockwise from top left: MODEL 1000, MODEL 1200, MODEL 2300, and MODEL 1250. Each is a ball-and-cage style heart valve, the upper two models with plastic balls and the lower two with metal balls. Model 2300 has a cage completely covered in white mesh cloth, while the three other models have cloth-covered rings only.