Just got off the phone with him....

Looks to me like the original joint boot had the metal ring, and its still on the inner pot. Looks to me like they roll formed the clamp onto the pot after they fitted it to seal in the grease.
The black paint on it is a good clue.
Needs to be cut off.
Told him to measure the overall inner boot clamp, and then the joint.
They should be close to the same diameter.
If not, I'd bet the original clamp is still on there!

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2009 Mercedes ML320 Bluetec