Will this fit across back seat?

[DogRocker]

...of a W123 300D?

Keyboard case that's 53" across...and still be able to close the doors of course.

[Rogviler]

If you raised it up on something above the arm rests then yes, your keyboard that looks suspiciously like a sniper rifle would fit. Otherwise the arm rests would interfere with it slightly.

[DogRocker]

...your keyboard that looks suspiciously like a sniper rifle...

I got the same reaction at the airport. I also have a soft case that's ~51" across. Maybe that would fit better. Thanks for the response.

[Rogviler]

Haha, it's a nice one though. You would only need about an inch less in length for it to fit just fine.