  Gravitational waves (GWs) from stellar-mass compact binary coalescences
(CBCs) are expected to be strongly lensed when encountering large
agglomerations of matter, such as galaxies or clusters. Searches for strongly
lensed GWs have been conducted using data from the first three observing runs
of the LIGO-Virgo GW detector network. Although no confirmed detections have
been reported, interesting candidate lensed pairs have been identified. In this
work, we delineate a preliminary analysis that rapidly identifies pairs to be
further analyzed by more sophisticated Bayesian parameter estimation (PE)
methods. The analysis relies on the Gaussian/Fisher approximation to the
likelihood and compares the corresponding approximate posteriors on the chirp
masses of the candidate pair. It additionally cross-correlates the rapidly
produced localization sky areas (constructed by Bayestar sky-localization
software). The analysis was used to identify pairs involving counterparts from
targeted sub-threshold searches to confidently detected super-threshold CBC
events. The most significant candidate ``super-sub'' pair deemed by this
analysis was subsequently found, by more sophisticated and detailed joint-PE
analyses, to be among the more significant candidate pairs, but not
sufficiently significant to suggest the observation of a lensed event [1].
