Let me preface this to say, lights are whatever you hook them up to be. True, A and E are the instrument lights, and light the face of the gauge by reflecting off the inside of the bezel. That probably why you see it lighting “F” in the plastic light holder at the bottom of the gauge.
Fibersteel lists these as replica 550 gauges, but they’re not. This is what original 550 gauges look like.
And according to type550.com, the two lights in the bottom of the tach are the signals, flanking what I assume is the blue high beam indicator. The combi gauge only has two lights, for alternator (red) and oil pressure (green)
Most “550 Replica Gauges” whether OG Brazilian VDO repros or Chinese copies are a weird collection of various VDO gauges with 2-3 lights in the tach and 4 in the combi gauge, something no Porsche ever came with AFAIK.
My early Beck came with Brazilian repros with a two-head arrow signal indicator in the bottom middle of the tach and red bullet lenses on either side. And 4 bullet lenses in the combi gauge, 3 red and one blue.
More modern repros have larger flat lenses for all the idiot lights.
These are the Indian-made repros that Greg sells, with icons listing the lights as (L-R) brake pressure (fluid) turn indicators, lights, and oil pressure, high beam, green (?) and alternator in the combi gauge
My best guess at your gauge wiring is that A and E, are instrument illumination judging by the appearance of the bulb sockets (and the fact that I don’t see any lenses there in your first pic) D is the +/- for the tach itself and 1&3 should be your L/R signal indicators but since they’re red and green, I’m assuming alternator (red) and oil pressure (green) and 2 is your high beam.
One thing that puzzles me is that C has the vertical line that I assume is the ground based on that same vertical line being between the +/- for the tach on the back of the gauge I posted. Another thing that puzzles me is that there appears to be a tiny red lens next to the right face plate screw about 7,000 rpm. Is that indeed a lens? Might be worth hooking up a 9V battery to some of those spade connectors to see if any of them light it. It would be pretty cool to have a shift light, although it so tiny I doubt you could see it in daylight.