I figured out the 3-pin and 12-pin pinout for adapter board 250-0472-00, used in Flir FC-T CCTV cameras.
I'm posting it here for anyone's reference.
Small 3-pin white port is for serial, bottom is GND, other two are TX and RX.
The 12-pin J7:
PIN CONN
2,10,11,12 GND
1 video+
7,8,9 power+
If any questions, you can ask.