Hi Martin,
I am a beginner at clock repair, and I mark the wheels. I use a scribe. I make a small notation of T1, T11, T111 etc on the time wheels, and S1, S11, S111 etc on the strike wheels. Important: I am not working on other peoples’ clocks. I am working on “learning” clocks, that is, inexpensive inop clocks I’ve obtained at rummage sales, or the NAWCC chapter meetings. Good luck!