2007 Model 100R. Came off of 07 Black Tacoma Dbl Cab Short Bed. Fits 2005+ models of the same nature (I'm assuming 2nd gens only, please correct me if I'm wrong, I'm not familiar with the changes Toyota makes over the years)
There is 4-5" of mounting space around the bottom of the cap, the 4 mounting blocks/hardware that came with it slide into the bed rail, align with holes in the bottom of the cap, and then a bolt is slid through. I assume you could use your own clamps if you don't have bed rails. There's a rubber gasket/seal underneath that keeps out moisture. There is also a hook up for its rear tail light. The cap locks with the rear handles.
Official page - http://www.leer.com/100rpage.html
Aside from a missing screen on left side, it's in great condition. Miniscule scratches from regular wear and tear, you have to look closely to find them. Stored indoors while not used. Have all paperwork, mounting hardware, keys, and touch up paint. $1100 new, yours for $450, firm. Cash only/Local Pickup. Located in Sharon, MA (25 mins south of Boston off I-95) Thanks for looking! PM me if interested!