SW series switcher (hood slopes back toward cab) in L&N livery (Family Lines at the latest).
My grandad made his living driving one of these. Once when I was about11 or 12 (48 years ago), he took me down to the South Nashville yards, put me in the right hand seat of such a loco and let me drive it about a hundred yards.
You can see why I simply MUST have one of these for the layout I am re- doing in a mid-1950's flavor.
The closest I have found so far is a unit from Athearn, but it is only a dummy and I want an operating one.