All M104 pans are not interchangeable with M103 pans. All W124 pans are shallower if it's an M104 pan (I have yet to see a mid sump M103 pan, so not sure on that one). It's about 10ish mm more shallow. This means that if you try and run a pickup from an M103, it will physically hit the bottom of the pan.

Again, the higher oil requirement in the head means that to run the same oil capacity (which they both have) that more of the oil is in the head at any one point in time, meaning to keep the same relative oil level the pan is shallower.

To your other question, all dates listed are engine production dates, as listed in the MB factory service manual for the M104. On many different setups they give an engine serial break point (as seen in the valve discussion), however on things like this they seem to just give an OH BY THE WAY, we changed things on 1/94.

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1993 190E 2.6 Sportline