Cents with and without Brenner's initials were struck at both Philadelphia and San Francisco in 1909. Coins struck at Philadelphia bear no mintmark; those struck at San Francisco were marked with an S. While almost 28 million Philadelphia VDB cents were struck, making them quite common, the 1909-S with Brenner's initials (commonly called the 1909-S VDB) is the rarest Lincoln cent by date and mintmark, with only 484,000 released for circulation. In 1911, the Denver Mint began striking cents with the mintmark D, and in most years in the following decades, all three mints struck cents. In 1916, Barber modified the design, causing Lincoln's cheek and coat to appear less wrinkled. This modification was done to extend die life.