S Herman wrote:

The LOC-D approach for SAN DIEGO/GILLESPIE FIELD (SEE) shows different
minimums for "GRIGG FM". There is an ident code shown for GRIGG, but
no frequency. Is the dot-dash-dot ident just the generic MM ident? I
can't find "GRIGG" listed as an airspace fix at airnav.com. Are the
higher minimums to be used for an approach in an aircraft without an
operating audible marker annunciation? What does "FM" stand for?
Airnav shows GRIGG as a Middle Marker. Thanks.

Airnav is wrong. It is an "airway's" fan or "Z" marker, and it is used as
a stepdown fix on that approach. In addition to the dot-dash-dot aural
ID, it would light the white light on your MB panel.

The original scheme was set when L/F Range stations, NDBs and ILSes were
the IFR nav system.

The white light was for either the "Z" marker that marked the cone of
silence of a range station or the same marker was used along the leg of a
range station for either a procedure turn fix or stepdown fix. Later, the
white light was pressed into service for the IM for CAT II ILSes, and for
applications like this one at KSEE where no other fix is available.