  We report metallicities for three $\sim$Gyr-old stars in the Milky Way
nuclear star cluster (NSC) using high-resolution near-infrared spectroscopy. We
derive effective temperatures from a calibration with Sc line strength, which
yields results in good agreement with other methods, and metallicities from
spectral fits to Fe I lines. Our derived metallicities range from -1.2 < [Fe/H]
< +0.5, a span of 1.7 dex. In addition we use isochrone projection to obtain
masses of 1.6 to 4.3 M$_\odot$, and ages assuming single-star evolution. The
oldest of these stars is 1.5 Gyr while the youngest and most metal-rich is only
100 Myr. The wide range in metallicity poses interesting questions concerning
the chemical evolution and enrichment of the NSC and adds to the evidence for
the presence of a young, metal-rich population in the NSC. We suggest that the
candidate intermediate-age, metal-poor ([Fe/H] = -1.2) star may be best
explained as a blue straggler from an underlying old population.
