Trim identification

Hi guys.

I'm a supercharger noob, so bear with me. I just bought a used SC-trim head unit. The tag only says it's a V-1, so my question is, how do I know I got an SC-trim and not any other? Any way to visually identify the impellers?

Thanks!

EDIT: Maybe this pic helps.

http://www.multier.com/images/misc/V...Impeller01.jpg

There should be a tag on the head unit. If not, I don't know how to tell them apart.