Hmm that is quite interesting, greenfield have always used the collar, right up until the last fastcut. My red one is the same, however i did just pull up the photo of the #2 machine and it appears to use nuts! Doesn't really mean much, still, indicates how early it is though i guess.
Wheel nuts are standard on the early rovers if that means much, i know theo worked for rover before greenfield, maybe he wanted to separate the machines a bit further.
