  In this note, we present spectral fits of the well-documented sloshing
cool-core cluster Zwicky 3146 ($z=0.291$), to test the existence of the highly
speculated 3.5 keV line. We report excesses at $>3\sigma$ significance at
$E=3.575$ keV, yielding a flux $F = 8.73_{-2.22}^{+2.17}$ $\times 10^{-6}$
photons cm$^{-2}$ s$^{-1}$, in \textit{XMM-Newton}, and $E=3.55$ keV, with a
flux $F = 10.0_{-2.96}^{+3.05}$ $\times 10^{-6}$ photons cm$^{-2}$ s$^{-1}$ in
\textit{Chandra}. We explore the possibility that the 3.5 keV excess is
correlated to the presence of cold gas within the cluster, based on optical and
sub-mm literature analyses. Following the launch of the X-ray Imaging and
Spectroscopy Mission (XRISM), high resolution spectroscopy ($\leq 7$ eV) will
reveal in unprecedented detail, the origin of this unidentified feature, for
which Zwicky 3146 should be considered a viable target, due to the strength of
the feature in two independent X-ray telescopes, opening a new window into
plasma or charge exchange studies in galaxy clusters.
