Markers and class lights

Before getting into a discussion here, we need to understand that class lights ("signals" in the rule book) are completely different from markers. Among fans there seems to be a lot of confusion on this issue, since both involved lanterns with various colored lens, or flags. But they had very different meanings.
So-called class lights (located only on the front of engines) had the same colored lenses in all directions, clear (white) for extras, green for advanced sections of scheduled trains, none for scheduled trains or the last section of multiple section scheduled trains. During the day white or green (or no) flags were used.
Markers, indicating the end of a train, had one red lens and three either green or yellow lenses, depending on the particular railroad and time. They could be located on the rear of a caboose, or on the pilot beam of an engine running backwards either light or as a pusher.
These lanterns could be rotated in their brackets so that when a train entered a siding and cleared the main (and the switch was aligned for the main) the lantern could be turned so that the green or yellow faced to the rear (in the direction of following trains). Class lights did not rotate.
Okay, a couple of caveats. One, the rules changed over time and between railroads. Secondly, my experience was on diesels which had a different kind of class light than steamers used. And finally, who knows how good my failing memory is. But I am looking at an old rule book (SP, February 15,1943).