Z' RESERVATION AT LEP2

We consider the possibility that one extra Z = Z' exists with arbitrar y mass and fermion couplings that do not violate (charged) lepton univ ersality. We show that, in such a situation, a functional relationship is generated between the deviations from the SM values of three lepto nic observables of two-fermion production at future e(+)e(-) colliders that is completely independent of the values of the Z' mass and coupl ings. This selects a certain region in the 3-d space of the deviations that is characteristic of the model (Z' ''reservation''). As a specif ic and relevant example, we show the picture that would emerge at LEP2 under realistic experimental conditions.