  Using the left-right symmetric model as an illustrative example, we suggest a
simple and straightforward way of constraining the $W'$ mass directly from the
decay of the Higgs boson to two photons. The proposed method is generic and
applicable to a diverse range of models with a $W'$-boson that couples to the
SM-like Higgs boson. Our analysis exemplifies how the precision measurement of
the Higgs to diphoton signal strength can have a pivotal role in probing the
scale of new physics.
