  An extension of the standard model of electro-weak interactions by an extra
abelian gauge boson is given, in which the extra gauge boson and the
hypercharge gauge boson both couple to an axionic scalar in a form that leads
to a Stueckelberg mass term. The theory leads to a massive Z$'$ whose couplings
to fermions are uniquely determined and suppressed by small mixing angles. Such
a Z$'$ could have low mass and appear in $e^+e^-$ collisions as a sharp
resonance. The branching ratios into $f\bar f$ species, and the
forward-backward asymmetry are found to have distinctive features. The model
also predicts a new unit of electric charge $e'=Q'e$, where $Q'$ is in general
irrational, in the coupling of the photon with hidden matter that is neutral
under $SU(2)_L\times U(1)_Y$.
