I read from other RC forum that if you switch on the SXX Stock Spec and it has no initial "beep" sound, it is the first version (they call it MK I) and if it starts with 2 beep, it is the update firmware version (known as MK II). You can only confirm that with all connection are done, including motor.
Some people from US sent their ESC directly to LRP Germany for fix ...
I will test mine this weekend and hope I got a good one ....