Dear Ivan:
3 pole connector, started to be used by year 1970 aprox, when the T16 signal,to coil was implemented
4 pole connector, never in use on a w113, this connector should come from a much later Mercedes like w116. Nevertheless you can give it an use on those cars if you want an AC system, which requires a 4th signal going in the vicinity of the Alternator to the 100C degree temp switch in the water thermostat housing.
Best regards
L.peterssen
Www.wiredoktor.com