Can you identify this piece of climbing gear?

Hi, I used to be a climber when I was younger before I injured my back, worked with a youth camp and took kids along the Blue Ridge Mountains to set up climbs and teach them the basics. However, in all that time I have never seen a piece of gear like this - albeit even though I could set up climbs and lead a safe outing I do not claim to be very knowledgeable past that. So if you could please help me identify this equipment below. I bought it from a man today who said it is used in repelling and some sort or descent. He didn't know much about the gear. I purchased it for 1$. So, could you tell me what it is? Each of these pieces move and those two blue pieces pivot out. I'm assuming that maybe its to weave a knot and than unhinge somehow but i'm not sure and would like to know more about it. Any help is greatly appreciated!

It's a rappelling device.

http://www.mtrsuperstore.com/products/rescuetech-rescue-rack-descender?variant=831872241&utm_source=nextag&utm_medium=cse&utm_term=shopify_US_340747673_831872241

It's a brake bar/brake rack. These days typically used by cavers for long single-rope descents and by mountain rescue teams for lowering heavy loads. The hinged bars allow you to set it up with varying amounts of friction, depending on the load. PMI makes or used to make them and may have setup info on their website.

Great! Thanks guys!

The moveable "bars" can be added or removed for more or less friction. In a long, long rappel(cavers may go hundreds of feet on a single line)the weight of the rope initial supplies alot of friction. As one descends, less rope weight is "braking" the friction device, thus more "bars" would be added to achieve the same level of friction. Hope this helps!