Is this a fan dial?

Its a dial that has 3 plastic inserts. Each of the plastic inserts has a slightly different shape in the center that ideally will fit the shaft of the control unit you bought it for. Example, the stem of my baseboard heater had a half-moon shape (pretty common). The plastic insert fit over that, and the dial it over the plastic insert. Problem solved. And the dial is cast metal, not cheap plastic.

It is a wall plate to cover light switches.