The OP has another thread about trying to troubleshoot a non-opening t-stat, so I presume he's trying to find a different way of measuring/verifying coolant temps seen by various sensors.

I'm not sure the CCU on the W123 has the info you're looking for. The climate control uses a cold engine lockout, but I don't think it has other coolant temp inputs. This page has some info on inputs to the CCU and their values: Middle-aged Mercedes Electrical Repairs

I think the info regarding coolant temps and the resistance of various senders exist, but I don't recall where I've seen it. I thought there was a thread at one time where a M-B tech explained that they used the 100 C hash mark to calibrate the sender by providing a specific resistance value to the temp gauge inputs.

The glow plug relay section in the manual has some values associated with coolant temp as measured by that sensor

0 C = 8200 ohm
25 C = 2440 ohm
80 C = 290 ohm

These values are more/less consistent with the same ones for the test for the CA EGR temp sensor (which may be the same one?).

20 C = 2.2-2.8 kohm
80 C = 290-364 ohm
100 C = 140-222 ohm