Some of the spectra have "EB", "EC", or "WB" in their file
names. What does this mean? The EB, EC, WB suffixes are tags
that were added to the standard DEEP2 maskname (typically a digit #)
by the Keck slitmask milling machine when those masks were made.
Those masks had been milled previously but either were not observed
(due to bad weather, etc.) or were observed under poor conditions, so
we opted to reobserve the mask. For a subsequent observing run, the
masks were remilled, rather than reusing the old masks, as dust on the
mask can create funkiness in the slit function, thereby making the
ends of the slits difficult to reduce cleanly. To distinguish
duplicate copies of the same slitmask, the Keck milling process added
an "A, B, C" to the end of the slitmasks name. This suffix was then
put into the header of the raw DEIMOS frame and carried along through
the DEEP2/DEIMOS pipeline. Yet another thing that I meant to clean up
prior to the release, but time did not allow.