What's the difference between a K4 4-6-2 (pre-war with Slat Pilot) and (post-war with modern pilot)? I have looked at pictures of the steam locomotives side by side and for the life of me can not see a difference. Am I blind? It's like one of those puzzles that you see in the comic strip where the cartoonist ask you to pick out the 6 differences between the two cartoons. I can do that---most of the time---but this one eludes me.