Made from flies homozygous for the malignant blood neoplasm mutation l(2)mbn (Gateff, 1980). Recent work using whole genome sequencing, transposon profiling and modENCODE transcriptome data (Han et al, 2021) attempted to shed light on the provenance of mbn2. The work clustered mbn2 together with S2-DRSC and S2R+ lines. The work raised the possibility that mbn2 is a divergent lineage of S2. Unfortunately, without data on the original fly stock from which mbn2 line was derived, it was not possible to ascertain. In a separate manuscript (Mariyappa et al, 2021), we note that it is possible to identify and distinguish blinded samples of mbn2 line from the S2 lines.