Do you know what year this model is from? If you have the box it should say. The only one I have seen dates from 2003.
The snipped wires are not unusual in a 3rd Rail model - all of mine have them, which I have always assumed reflects the fact that 3rd Rail had some different electronic components from standard TMCC. I think that these were early ERR. Plus some steamers had TAS EOB rather than Odyssey.
The Mars Light function has me stumped as the only one I have with anything similar (an FEF-3) doesn’t function in the way you describe, but I can see that if it’s connected to the motor circuit, it might increase in intensity with speed. As TMCC did not always have a Mars Light output, unlike some DCC boards, but usually a separate lighting PCB, the function might have been included based on an ad hoc wiring method.
You can always ask Scott Mann himself via email if you need more help.
