Idle...speakers in the kick panel were only installed if the radio was stereo. In 1967, the car was likely fitted with an AM/FM Mono unit (like I have in my 250SL, built in July 1967).

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All the best,

J. P. Mose
1968 250SL
1970 280SE 3.5 Cabrio
1987 560SL
1990 560SEL