I was powering it with a little more than just enough to light it @ 2.1v, hardly enough to form any noticeable unidirectional emission. A little more power, and a huge contrast forms between light going in many directions and the main beam. this one was supposed to run on 4.5v of button batteries. @4.8v and point blank range shining on a black sharpie spot on my skin, no lens in the way, I felt no heat at all, but maybe I could if it was focused at that distance (about 1mm from the diode). Just putting the <5mW red laser power in perspective.
My only problem now is finding the right size pen or junk laying around to make a pen host.