Are you absolutely sure you know what CCPM is?

If you want to get technical, one is mechanical (all the mixing done on the helicopter via levers and bellcranks). The other (eCCPM) the mixing is done electronically on the radio.

The main difference is that the mCCPM has a bunch of bellcranks and mixers to achieve it's goal. On the eCCPM heli, you will have the servos connected directly to the swashplate.

It is hard to explain these days because most, if not all of the newer helis are either eCCPM or mCCPM. Years ago there were helis that were not CCPM. The Concept line of helis built by Kysho, comes to mind. Find one of those and you will immediately notice the difference. Otherwise I would not worry. Nowadays I worry about eCCPM and mostly make the assuption that the rest are mCCPM.

Rafael