Greetings...
I believe most of them are reflecting which division that particular squad belongs to. Example, D2 would be District 2,
D1 District 1
D2 District 2
D3 District 3
D4 District 4
D5 District 5
D6 District 6
D7 District 7
TEU would be Tactical Enforcement Unit
NTF would be the Neighborhood Task Force.
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Tim