The sedan, coupe, and wagon all have a rear sway bar, and all use the same links. The picture you posted is the correct part for all 123s, as far as I know. If they're worn, they will rattle. If one is broken, it will allow the sway bar to rub the inside of the wheel in turns.

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Dale
'67 Volvo 122
'79 Rabbit Diesel
'79 M-B 300TD
'82 M-B 300D
'83 M-B 300CD
'85 M-B 300TD
'86 Isuzu P'up TD
and a couple of Hondas