Does anybody know how to identify an ECU once it is out of the car?

You can Identify the ECU by the part number. For example

These are the part numbers for the BLUEBIRD ECU.
(NOTE: REMEMBER THERE IS A DIFFERENCE BETWEEN AT & MT)

U12 SR20DET AT 4WD/AWD 23710-79E10
U12 SR20DET MT 4WD/AWD 23710-79E01

Here is the part number for the Pulsar GTI-R ECU.
(NOTE: PULSAR GTI-R ONLY CAME 4WD/AWD NO WORRIES HERE)

RNN14 SR20DET MT 4WD/AWD 23710-54C00

Here is the part number for Pulsar GTI-R MAF SENSOR

RNN14 SR20DET M/T 4WD/AWD 22680-54C00