This lower dash panel cover or trim piece was removed from a US-specification 1979 Mercedes-Benz 300CD. It was located just below the steering column and dashboard, and above the driver's knees.
This part may fit other early W123 vehicles, possibly including 200, 200T, 230, 230C, 230T, 230E, 230CE, 230TE, 250, 250T, 280, 280C, 280E, 280CE, 280TE, 200D, 220D, 240D, 240TD, 300D, 300CD, and 300TD.
I believe that later models had a similar panel that attaches with screws hidden under little plastic covers or caps; this piece attaches with metal clips (which are included, as pictured). The two styles are not interchangeable.
Very good condition, no cracks.
Color is black. Part number is 123 680 09 17 or 1236800917.