The BDSM community has always had an interest in the world of medicals. There are many pieces of equipment that have been borrowed and used to sexually excite.
Theis one of these things. Designed by Robert it purpose is to test for nerve reactions. The wheel has pins along the rim which causes a sensation when rolled over skin. The pins do not puncture the skin.
The pinwheel is best used on a sub when they are bound. Running it over the sub causes them to squirm. The pins are not sharp enough to damage but cause that confusing feeling between pleasure and pain.