Personal communication to FlyBase from M. Gatt & M. Ashburner.
anon-3Ba is  EG:100G10.7  on basis of size & restriction map.
anon-3Bb is  EG:100G10.5  on basis of size, restriction map & direction.
Note that the direction of transcription of anon-3Ba is opposite to that
of  EG:100G10.7 . However, everything else fits (indeed the match between
the restriction maps is excellent, and, the direction of transcription
of anon-3B1.2 (as 0.9kb transcript) shown in the relevant figure,
figure 2 of Reddy et al. (1984) Cell  38:701-710 , is wrong, since
even the database accession says that it is off the opposite strand to per
and not the same (as in fig 2 here). So we have little concern that the
authors got the direction of transcription of the 2.7-kb RNA (aka anon-3Ba)
wrong.
In conclusion the revised gene order statement should be:
per+ anon-3B1.2-  EG:100G10.7-   EG:100G10.5-