  We report on the experimental investigation of the fluctuation properties in
the resonance frequency spectra of a flat resonator simulating a dissipative
quantum billiard subject to partial time-reversal invariance violation (TIV)
which is induced by two magnetized ferrites. The cavity has the shape of a
quarter bowtie billiard of which the corresponding classical dynamics is
chaotic. Due to dissipation it is impossible to identify a complete list of
resonance frequencies. Based on a random-matrix theory approach we derive
analytical expressions for statistical measures of short- and long-range
correlations in such incomplete spectra interpolating between the cases of
preserved time-reversal invariance and complete TIV and demonstrate their
applicability to the experimental spectra.
