You can perhaps tell by looking at the wiring harness and other dash components; the rallye instrument cluster used a different harness (wires for the tach, clock, etc). I have been told the light bar is different as well which I suspect has different placement of the lights than a standard dash. If someone did a complete swap, you will never know but most people wouldn't have swapped the harness. A standard harness is easily made to work with a rallye dash by running a few wires, so there wasn't much of an incentive to replace it with the rallye one.
I would assume that the heater control panel matched the rallye dash (assuming the car you have has a rallye instrument cluster in it now).