Friend of mine brought this over to my house, his dad gave it to him.

Don't know anything about these things, and I'm not having much luck finding it in my Blue Book.



How old is it? What's it worth?

Colt Army Special.  Forerunner to the Official Police.  Serial number dates it as 1919.  Grips aren't original, of course.  Army Special was just a Colt marketing ploy, the Army didn't actually issue these.  Good solid revolver.  Nickel finish may or may not be original.  

Value on old Colt revolvers has been all over the place in recent years.  Strictly as a guess I would probably start in the upper 300 range.