I think as above you found a goof.
3 things should indicate proto-48. First the wheel gauge - and since yours fits the NMRA gauge which is scale 5 feet, it is not right. the wheel gauge should be narrower approximate 4.177 inches, not 4.25 inches.
The second thing is the wheels should be narrower. Not sure, but at least 30% I think.
The third thing is the flanges on the wheels should be smaller. Again I don't know how much, but noticably so when compared side by side.