Seems like a silly thing but I've never been sure how to check the exact version of CME running. "show telephony" will do it. I'm either overlooking something in the GUI or it's not there. On a particular router I'm messing with the "About" screen doesn't show anything. Maybe that's broken.
It's important to be sure of the version running as there are dependencies for phone models and CUE versions.
Anyway...saved for future reference.