Is there a trick to removing the wiring harness from the ignition barrel?

When I bought my '84 300D the PO told me that the barrel had been replaced with a non-MB igition barrel and that accounted for the buzzer sounding when you open the door even if the key is not inserted.

Well the barrel is obviously a MB barrel. But perhaps from a later model year. Anyway I went to remove the barrel for closer inspection and couldn't get the wiring harness to come off. I squezed, pry'd and cussed to no avail. So.. whats the trick?

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'84 300CD Turbo 132k (Anthracite Grey) - WVO - My daily driver - Recently named coo-coo-coupe by my daughter.
'84 300D Turbo 240k (Anthracite Grey) - Garage Queen
'83 300D Turbo 220k (Orient Red) - WVO - Wifes daily driver

I'm not a certified mechanic, but I did stay at a HolidayInn Express last night.