Basic Book Laser Pistol Components

I'm making a 3D model of the laser pistol in the Alpha Dawn basic rule book.   There appears to be a switch at the top of the grip where the thumb could slide it towards the trigger.  I believe this is the safety switch.  To the right of this switch is another possible switch or lever at the top of the grip and just under the round knobby thing at the back of the gun.  What is this thing / lever / switch? <div><br /></div><div>Also where is the SEU clip on thus gun?  Is it the long round knobby thing at the back of the gun? </div><div><br /></div><div>How does one adjust the SEU setting on the gun?</div><div><br /></div><div>What other features and components do you guys see in the drawing of the laser pistol? </div>