Just bought a Night Guard 315 (pic)

[XDmGlocks&w]

So I just bought this 315NG from a guy that bought it brand new a few years ago, never shot and hid it in his safe till he forgot about it.
He sold it too me for a steal of a deal after finding it hiding in the back of his safe. Freakin gun is amazingly clean of course with all the material that you would get when he bought it new.

My question is this, what in the hell is the meaning of the 3 white dots on the left side of the gun? I see them on all of the Night Guards that I have seen but do not know the meaning of them.

[XDmGlocks&w]

Now that I think about it I would also like to know how many of these were made and from what I understand they no longer make them.
Anyone have an idea what this might be worth in New condition?

Too shoot or not too shoot?

[XDmGlocks&w]

so if I flip it over they will line up with pins?
How many wheel guns have this and what is the real purpose?