It's a 1983 W123 300TD. I just don't know if it's best to keep the frame attached which involves removing the four I think screws (not sure how you get a screw driver in that last screw with roof panel in the way though). Or, if you just undo the hex bolts from the bracket and remove just the panel (but it's obvious they do have adjustments to those bolts).

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1983 W123 300TD US spec Turbo engine, with Euro bumpers and manual climate control, and manual transmission.