  We report the observation of a possible optical counterpart to the recently
discovered X-ray source NuSTAR J053449+2126.0 (J0534 in short). We observed the
source location using the 1.5-m Telescope (RTT150) to search for an optical
counterpart, and detected a possible optical counterpart and analysed its
spectrum using the $B$, $V$, $R$, and $I$ images of J0534, and found that the
possible optical counterpart of J0534 is likely to be a long-known optical
source, namely PSO J083.7063+21.4333. However, this source has been
misclassified as a star rather than being an extragalactic source. We
determined the source distance accurately for the first time based on our
spectral analysis. J0534 could be a high-redshift ($z\simeq2.2$) member of an
Active Galactic Nucleus (AGN) sub-group identified as quasars. Our analysis
favours an accreting black hole of mass $\sim 7\times 10^8 M_{\odot}$ as a
power supply for the quasar. Further observations in optical and other
wavelengths are needed to confirm its precise nature.
