The 1915 Lincoln Cent is very scarce as a Matte Proof, especially with full Red color. By 1915, interest in Matte Proofs waned and the number of coins sold decreased steadily until they were discontinued after 1916. Collectors simply did not warm up to the unusual finish on Matte Proofs.
In 1915, the Mint made 1,150 Matte Proofs, down from a high of 4,118 Matte Proofs in 1910.
The key to value and desirability with Matte Proofs is a combination of color and spotting. The redder the color and the cleaner the surfaces, the more valuable the coin.