Yes ch1 is 70mm bore cl9 is 64mm
But i run atr disc's with spoon calipers on my cl7,with no issue.i dont think it matters
As i said measure the disc,if you have less than 25mm thickness then they are probably cl9
If they are more than 25mm they will be atr disc's.its very unlikely you will have worn over 3mm out of a set of disc's.as atr are 28mm with a wear limit of 26mm