I'm running Ubuntu and Gnome, but this should be generally relevant to any system using X11.

I had a look at the source of the Gnome tools that read monitor information. They all use the X RandR (Resize and Rotate) library under the hood to gather monitor information

The xrandr command line tool shows the raw data provided by your monitor

$ xrandr --verbose
Screen 0: minimum 320 x 200, current 1280 x 1024, maximum 1280 x 1024
VGA connected 1280x1024+0+0 (0x3c) normal (normal left inverted right 
+x axis y axis) 338mm x 270mm
    Identifier: 0x3b
    Timestamp:  33753
    Subpixel:   unknown
    Clones:    
    CRTC:       0
    CRTCs:      0 1
    Panning:    0x0+0+0
    Tracking:   0x0+0+0
    Border:     0/0/0/0
    Transform:  1.000000 0.000000 0.000000
                0.000000 1.000000 0.000000
                0.000000 0.000000 1.000000
               filter: 
    EDID_DATA:
        00ffffffffffff0010ac0ba0554a4632
        110f010368221b78eecaf6a357479e23
        114f54a54b00714f8180010101010101
        010101010101302a009851002a403070
        1300520e1100001e000000ff00553439
        333135344b32464a550a000000fc0044
        454c4c204531373346500a20000000fd
        00384b1f500e000a2020202020200099
[download]

The EDID_DATA is particularly relevant to us. The read-edid project has utilities that turn the EDID information into something we can use:

$sudo get-edid 2>/dev/null| parse-edid 2>/dev/null| grep ModelName
    

ModelName "DELL E173FP"
[download]