I agree that is a big backup light. No problem seeing behind that loco!!!
Some of those pre- and post-war locos could pull a lot of cars - they had weight and power and if restored are remarkable, like that one.
Not to diss the old locos - I have some of them in my trainroom and love them, but what I like about modern locos is that they will pull as many cars while running at only a scale 10 to 20 mph, whereas the older locos only had lots of power at higher speeds.