Hi applecore5:
It's not what you think, get your filthy mind out of the gutter!
I think it's a scalp massager, looks like a dusting brush but with soft plasitc teeth to invigerate the scalp. Kirby had one and called the 'massage cup,' Filter Queen also had one.
Other uses for this thing is to put it on the long wand and unscrew a light bulb, or turn it in-side-out, plastic points down on the onside, to unclog a drain. In this case the vacuum needs to be in blower mode. Slip the massager thingy on the hose, and force the clog down the drain. Problem is, the damned thing didn't work for that!
Like several other 'gadgets' designed as a selling feature, it was little more than a gimmick! An old fashioned hair brush, or a comb works just as good.
If I find a picture of one on my attachment wall, I'll post it for you.
Alex Taber.