Quick Draw artist

My friend Fred Patten owns this original Quick Draw McGraw painting (click on it above, or here, for enlarged image) created for a frame tray puzzle. Both of us are stumped as to who may have painted it. I’m no expert on merchandising art, but it doesn’t look like the usual suspects at Western Publishing to me (Pete Alvarado, Mel Crawford, Hawley Pratt, etc.) – or is it? Anyone have any theories?