Hmmm... Mine all looked the same and the mechanic that put on the locking nuts just took one off each wheel and put the locking ones in. there was no comment at all on the fact that those that were on the car were locking ones - he just used a normal socket and wrench to make the change - how do you tell the one that is locking assuming that there is one in the first place? They all look the same to me nuts that fit on a stud.
@ Paul Churchley
My keyed socket is now in the boot - I know that does not help - I just could not resist the comment
Today, my dealer supplied and fitted a set of locking wheel nuts free of charge, worth mentioning if your Ampera does not have them. They are black with a slightly bigger hexagon, which I queried, was told they are covers and come off exposing the familiar locking nut underneath.