There are a number of RailKing accessory items that are actually 'S'. They are made with tooling MTH picked up when Flyer was selling it to try and stay afloat before they finally went under. Most of it has been shifted from RailKing 'O' to the new MTH 'S' catalog.
The Gilbert Gallery has pictures of the originals if you want to compare to the MTH 'S' catalog.