When not mounted, the four arm bottom rim frame will rotate when holding the body of the marker light. When set in its bracket on a caboose, the body would be rotated to change aspects, as the bottom rim would be fixed in the holding bracket.
That way, it was much easier and safer to change the aspect of the marker or classification lamp by rotating the body of the lamp.
With the four arm frame rigidly fixed to the body, a crewman would need to take the marker down off its bracket, turn the lamp around to show the desired aspect, then hoist it back up into the bracket.
As you know, its not exactly a lightweight piece to hang in an outside corner bracket, especially at night in bad weather.
S. Islander
