The C version of the RNS came as a star button and also as a speaker/i button. So if it's a non star button then it could be an A, B, or C. Pull the unit and find out for certain would be my advice.
The disc you have for no battery drain will work on the two firmwares I've pointed out to you as well, so battery drain shouldn't be an issue, although I'd suspect that the car has had the gateway done.