i have both green and red Five-Fifteen Limited coaches, but i don't think i've ever seen a green engine. according to a TCQ article, the body coupler cars and engine were the earlier version followed by the slightly more durable construction with a floor and separate, sliding tab & slot couplers. the later year 'deluxe' sets came with two vs a single car and the Little Dynamo transformer...
...one of my three favorites. (note: bottom tabs are still straightened from my initial servicing and awaiting a period power cord until i seal it up again.)
one car sets were packed with a single 19" circle of track while the deluxe sets could form a small figure-8 layout.
fun little motorized set.
cheers...gary