Hi, all!
Good day to you!
This is the way to get ESN of the MCU/SMC/RSE6500 device.
MCU
Login to MCU web the default user name is admin and password is Change Me and Feedback the ESN of the Device to us as the following picture.

SMC
Login to SMC web the default user name is admin and password is Change Me and Feedback the ESN of the Device to us as the following picture:

RSE6500
Login to RSE web the default user name is admin and password is Change Me and Feedback the ESN of the Device to us as the following picture:

Thanks!