No need to bust the Glass. When I locked Keys inside of the Car the Auto Club came out and used a plastic wedge to pry the Door out a little. They then inserted something like a Blood Pressure between the Door and Frame and squeezed the Bulb and inflated the That Thing untill there was enough room to stick their Wire Tool in and pull the Door latch Lock.
Note: that was not on a Mercedes.

The Tow Truck Driver sent by AAA opened the Car.

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84 300D, 82 Volvo 244Gl Diesel

On your w123? I'd never think something could fit in the space that the door and door frame leave.

It was not on the 123.
But, like I said the Tow Truck Driver drove a Plastic wedge between the Door and the Frame/Pillar at the top of the Door.

I don't have a plastic Wedge to try that so I can't say if it will work or not. Part of My point was that the Driver knew what He was doing.

OK I just tried this with a Screwdriver and folds of Newspaper over the exterior Paint so I would not scratch it and I could with out much effort (I did not want to damage the paint so I did not push it hard) on my W123 open a 1/4 inch gap between the Rubber Molding and the Pillar.

That would be enough to get a Coat Hanger throug; and I have used a Coat Hanger on another Car before so I have some experience at that; extremely frustrating but it finally worked.

I am guessing if I had the proper Tool I could open a larger Gap.

Added that was the Rear Pillar on the Front Door at the top.

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84 300D, 82 Volvo 244Gl Diesel