Here are some things to determine that this Mikado is in fact a K-Line USRA Mikado and not a MTH one. But first I want start this off by saying that I have both K-Line NYC Mikado's (NYC 1838 and NYC 1849 (K3670-1849W) ) but anyway lets get started.
1) On a K-Line Mikado, the coal load is molded into the tender shell, whereas the MTH Mikado have real coal load.
2) The tether on the K-Line scale steam engines is thinner looking then the MTH tether. Also the plug on tether are different looking too.
3) The MTH Mikado should have the battery charging port underneath as well as the volume pot, at least that is what I believe. Now on K-Line's Mikado's, there is no charging port because the engine has TMCC and not DCS. The volume pot on the K-Line Mikado is underneath the water hatch on the tender. Next to volume pot is the Railsounds - Signalsounds switch which the MTH Mikado doesn't have.
4) In the pictures, the engine is sitting on the track with power on and the Lights on with no sound on. <- That is standard TMCC or early Legacy practice. When a MTH engine is sitting on the track with power on, it's light don't come on do it seeing the DCS signal. <- That is standard MTH operating practice.
5) The coil on a MTH Proto-Coupler looks different than what the coil on a Electro Coupler is.
6) Different pilots on the front of each engine as what Dave C said above.
7) The boilers between the MTH and K-Line Mikado's don't look the same. The MTH model, number 20-3051-1, looks more like a USRA Heavy Mikado where as the K-Line one looks like a Light Mikado.
8) Lastly the supposed MTH Mikado in question came out in 2001 where as the K-Line one came in 2003.
With that all being said, I strongly believe that the Mikado Bruce has is a K-Line model and not MTH.