Lincoln matte proof cents are very scarce as a group, and the 1915 proof cents are especially challenging. Relatively few were made, especially in comparison to the higher-mintage pieces of the era, such as the 1909, 1910, or 1913 matte proof cents. The 1915 proof cent is especially rare with full Red color. Collectors paying top premiums for pieces with nice Red color, few spots, and nice overall eye appeal.