Removing Garrett T3 wastegate cover

[5cylinder]

As I plan out the rebuild of the Garrett T3 turbocharger on my 1985 300D (617.952), I would like to open the wastegaste component (picture below) to check the condition of the diaphram (or just replace it after 37 years) and check if the assembly inside moves freely or not.

The problem:
I have thus far been unable to remove the cover though I can spin the cover fairly easily about 90 degrees. On close inspection with a magnifying glass, I'm not seeing any sort of a clip or the like that holds the cover in place though maybe I'm overlooking something. YouTube videos and parts diagrams don't seem to show anything holding the cover in place. Perhaps the cover is just being held in place by 37 years of carbon buildup and oil?

I'm being cautious and not forcing anything. If anyone can give me some advice on how the cover should come off, that would be helpful. Thanks-