I don't know much specific info on the Unis but that looks like an older power unit with newer head. I have seen a couple that were entirely gray/light gray. which i think was early 90s maybe I know i seen it in one of my Oliver mags cause new idea was teamed up with White.
I think they are a neat machine, especially when you have all the different attachments. Theres a farm by Clevland, mn that has a real nice Uni collection.