I suppose this thread would be the best place to ask, but there's something I've always wondered. I have the ERTL model kit of the Excelsior from decades ago, and in the impulse engine area, they provided *three* clear red pieces for the engines. Two were narrow rectangles and went where you'd expect them to, but the third was nearly square and went in the trench between the other two. It was also a lot further forward, about the same fore/aft location as the aft end of the "fins" on top of the impulse engine assembly.
I don't ever remember any Excelsior class having a glowy-bit located there, so where on Earth did they get the idea to put one there? It's not as if it was just an extra bit, it was included in the instructions too.