The only way you can find out for sure is go to a tailor, if you have access to the Alpha and Omega costume pieces and auras, then you have the GR item pack or the Complete Collection. The early powerset access pre-purchase version didn't come with those.
edit: An even faster way is to see if you can do any of these stances:
/e stancehero1
/e stancehero2
/e stancevillain1
/e stancevillain2
Is there any way for me to find out if I have an Item Pack or which version of GR I bought? I'm pretty sure I have a few of the Mutant Costume pieces, but I don't remember any of the emotes...