ratio, wavelength range), while codes $-$93 and $-$94 correspond to data quality issues (i.e., slitmask design issues, detector issues). While in DR1 we distinguished between these four failure modes, for many analysis purposes, considering just the two general categories will be sufficient.]{}

Failure code $-$91, the most common failure code, generally indicates that the signal-to-noise ratio of the data was insufficient for redshift determination. Indeed, considering the 131 DEIMOS-observed sources in COSMOS with this failure code, 122 (93%) were *anticipated* to fail based on our estimated exposure time needed to get a redshift. As with low-confidence redshifts, sources for which we failed to find a redshift are not included in this data release.

[@c@]{}\

\[figure:specz\_somz\]

Serendipitous Sources
---------------------

We measured the redshifts of 134 serendipitously detected sources that happened to fall in slits with primary C3R2 targets. The coordinates of these sources were identified and they were matched back to the survey catalogs. The redshifts for these sources are included in our published catalog.

Literature sources
------------------

Some (unintentional) overlap with literature redshifts allows a check on our results. In COSMOS and EGS we observed 38 sources that have previously existing high-quality redshifts. Most (24) were serendipitous detections. We find 