[[File:3M Serial Num Label A.png|400px|thumb|right|Label "A"]]
[[File:3M Serial Num Label B.png|400px|thumb|right|Label "B"]]
[[File:3M Serial Num Label C.png|400px|thumb|right|Label "C"]]
[[File:3M Serial Num Label D.png|400px|thumb|right|Label "D"]]
[[File:3M Back - Old.jpg|400px|thumb|right|Back Door - Old Logo]]
[[File:3M Back - New.jpg|400px|thumb|right|Back Door - New Logo]]
This is a list compiled of all known 3M M-131 serial numbers from forum members. Also noted is the body color (and, if different, visor color). Note that doors were always flat black. There were several versions of the Serial label, and two versions of the back-door logo.

{| class="wikitable sortable" style="text-align: center;"
! data-sort-type="text" | Username!!data-sort-type="number" | Serial #!! data-sort-type="text" | Body/Visor Color!! data-sort-type="text" | Logo Style!! data-sort-type="text" | SN Plate Style !! class="unsortable"| Signal Notes
|-||StevenRosenow||108910||||||
|-
|Texas_Signal_Fan||115332||Yellow||||||
|-
|Texas_Signal_Fan||115333||Yellow||||||
|-
|Texas_Signal_Fan||115334 ||Yellow||||||
|-
|StevenRosenow||182818||Yellow||||||
|-
|StevenRosenow||182820||Yellow||||||
|-
|StevenRosenow||182821||Yellow / Black||||||
|-
|StevenRosenow||182829||Yellow||||||
|-
|bus1037||189220||||||||
|-
|bus1037||189221||||||||
|-
|bus1037||189222||||||||
|-
|bus1037||189223||||||||
|-
|StevenRosenow||200034||Green||||||
|-
|StevenRosenow||200035||Green||||||
|-
|StevenRosenow||200036||Green||||||
|-
|busman_49||211442||||||||
|-
|busman_49||211443||||||||
|-
|busman_49||211444||||||||
|-
|jmfirefighter20||214491||||||||
|-
|jmfirefighter20||214492||||||||
|-
|jmfirefighter20||214493||||||||
|-
|EPAC-EPIC-MARC||237731||Yellow||Old||C||
|-
|EPAC-EPIC-MARC||237732||Yellow||Old||C||
|-
|EPAC-EPIC-MARC||237733||Yellow||Old||C||
|-
|StevenRosenow||237734||Yellow||||||
|-
|StevenRosenow||237735||Yellow||||||
|-
|golfnguy||256395||||||||
|-
|golfnguy||256396||||||||
|-
|golfnguy||256397||||||||
|-
|golfnguy||256398||||||||
|-
|golfnguy||256399||||||||
|-
|justinwebb||257118||||||||
|-
|justinwebb||257121||||||||
|-
|justinwebb||257122||||||||
|-
|justinwebb||257123||||||||
|-
|justinwebb||257124||||||||
|-
|StevenRosenow||262786||||||||
|-
|StevenRosenow||262787||||||||
|-
|Pyth||290604||Yellow||Old||A||align=left|[http://www.flickr.com/photos/98823378@N08/sets/72157634660596999/ Flickr]
|-
|Pyth||290605||Yellow||Old||A||align=left|[http://www.flickr.com/photos/98823378@N08/sets/72157634660596999/ Flickr]
|-
|Pyth||290606||Yellow||Old||A||align=left|[http://www.flickr.com/photos/98823378@N08/sets/72157634660596999/ Flickr]
|-
|3Mfanatic||296153||Green||Old||A||Originally ordered by City of Portland, Oregon
|-
|3Mfanatic||296154||Green||Old||A||Originally ordered by City of Portland, Oregon
|-
|3Mfanatic||296155||Green||Old||A||Originally ordered by City of Portland, Oregon
|-
|justinwebb||302922||||||||
|-
|justinwebb||302923||||||||
|-
|justinwebb||302924||||||||
|-
|coyttl||314373||Yellow||New||B||align="left"|Signal 1 (from VA)
|-
|coyttl||314374||Yellow||New||B||align="left"|Signal 1 (from VA)
|-
|coyttl||314375||Yellow||New||B||align="left"|Signal 1 (from VA)
|-
|coyttl||289855||Grey(*)||Old||A||align="left"|Ped Signal 2 (from DC)
|-
|coyttl||289856||Grey(*)||Old||A||align="left"|Ped Signal 2 (from DC)
|-
|coyttl||181886||Grey(*)||Old||C||align="left"|Signal 3 (from DC, currently M-131R)
|-
|coyttl||181887||Grey(*)||Old||C||align="left"|Signal 3 (from DC, currently parts)
|-
|coyttl||186191||Grey(*)||Old||C||align="left"|Signal 3 (from DC, currently parts)
|-
|?||314388||||Old||New Plate||align="left"|Recently Sold
|-
|?||314389||||Old||New Plate||align="left"|Recently Sold
|-
|Blue245Ti||316101||||New||New Plate||
|-
|Blue245Ti||316102||||New||New Plate||
|-
|Blue245Ti||316103||||New||New Plate||
|-
|MacSignals||279334||Grey(*)||Old||C||align="left"|Signal 1
|-
|MacSignals||157939||Grey(*)||Old||C||align="left"|Signal 1
|-
|MacSignals||10458||Grey(*)||Old||?||align="left"|Signal 1 (Label has M-131PP or M-132PP)
|-
|MacSignals||268567||Grey(*)||Old||C||align="left"|Signal 2
|-
|MacSignals||164275||Grey(*)||Old||C||align="left"|Signal 2
|-
|MacSignals||182663||Grey(*)||Old||C||align="left"|Signal 2
|-
|MacSignals||229891||Grey(*)||Old||C||align="left"|Signal 3
|-
|MacSignals||157940||Grey(*)||Old||C||align="left"|Signal 3
|-
|MacSignals||162331||Grey(*)||Old||C||align="left"|Signal 4
|-
|MacSignals||217376||Grey(*)||Old||C||align="left"|Signal 4
|-
|MacSignals||217374||Grey(*)||Old||C||align="left"|Signal 4
|-
|MagnetBoy||316511||Grey(*)||New||B||align="left"|Signal 1
|-
|MagnetBoy||316512||Grey(*)||New||B||align="left"|Signal 1
|-
|MagnetBoy||316513||Grey(*)||New||B||align="left"|Signal 1
|-
|MagnetBoy||164273||Grey(*)||Old||C||align="left"|Signal 2
|-
|MagnetBoy||117255||Grey(*)||Old||C||align="left"|Signal 2 (M-133 Label)
|-
|MagnetBoy||173404||Grey(*)||Old||C||align="left"|Signal 2
|-
|MagnetBoy||114115||Grey(*)||Old||D||align="left"|Signal 3
|-
|MagnetBoy||114116||Grey(*)||Old||D||align="left"|Signal 3
|-
|MagnetBoy||120445||Grey(*)||Old||?||align="left"|Signal 3 (M-132 Label)
|}

* (*) - Some 3Ms were painted grey by the DC DOT, these are lighter in color and have colored doors. 3M Powder Coated some signals, which are a darker grey and have flat-black doors.