Df(2R)Sema-2b-C4 was generated by FLP-mediated recombination between P{XP}d00791 and PBac{WH}f05499. The location of P{XP}d00791 at 53C4, 2R:16386400 (R6) is given in http://flybase.org/reports/FBti0054202.html, but the entry for PBac{WH}f05499 (http://flybase.org/reports/FBti0052389.html) does not currently give a sequence location. If you BLAST the flanking sequence (CZ488090), there is one genomic location that matches the description in the paper (http://flybase.org/reports/FBrf0217575.html). It's 2R:16451895 (R6) at predicted band position 53C5. This would give Df(2R)Sema-2b-C4 the breakpoints 53C4;53C5, 2R:16386400 ;16451895 (R6).