  We consider the collider signals arising from kinetic mixing between the
hypercharge gauge boson of the Standard Model and its twin counterpart in the
Mirror Twin Higgs model, in the framework in which the twin photon is massive.
Through the mixing, the Standard Model fermions acquire charges under the
mirror photon and the mirror Z boson. We determine the current experimental
bounds on this scenario, and show that the mixing can be large enough to
discover both the twin photon and the twin Z at the LHC, or at a future 100 TeV
hadron collider, with dilepton resonances being a particularly conspicuous
signal. We show that, in simple models, measuring the masses of both the mirror
photon and mirror Z, along with the corresponding event rates in the dilepton
channel, overdetermines the system, and can be used to test these theories.
