outer space heater?

I was down in my garage this afternoon, putting some stuff away. In one of my private storage closets — to which I should mention only I have a key — I found this thing.

What the heck is it? Is it a heater? ‘Cause it looks like a heater, but it doesn’t look like one I’ve ever owned. Where did it come from? Who put it in my closet, and when and how?

Hmm. It looks vaguely familiar, but it ain’t mine. Mighty floggin’ curious, you ask me.