short observing campaigns [@Rod2016]. If, in addition, a lensed supernova is of Type Ia, extra constraints from the standard candle nature come into play. This can be used to measure magnification in an independent way [@Rod2015] and thus provide additional constraints on the lens model. This extra information can potentially narrow down inherent degeneracies in lens models which leave all lensing observables invariant, except the time delay [@Sch2014]. The unresolved degeneracies are the main source of potential systematic errors in cosmological constraints obtained from time-delay observations [@Kol1998; @Ogu2003].

Strongly lensed supernovae will be found in large numbers and in a more automatic way in ongoing and future transient surveys [see e.g. @Diego2018]. Two possible strategies for finding plausible candidates can be considered. One can search for multiply imaged supernovae [@Ogu2010a] or highly magnified (unresolved) transients [@Gold2017]. The former probes a unique feature indicating unambiguously the lensing nature of a candidate. The latter approach is less direct and involves an estimate of how much brighter an observed supernova is compared to a fiducial reference supernova, as it would have been observed in the lens galaxy (or the apparent host galaxy). Atypically bright supernovae in this case would indicate a high chance 