I doubt a '92 SL will ever do well, maybe an AMG version or one tuned to the max by Brabus. There are just so many of them. E320 cabriolet hold there price pretty well, a nice one is still around $20K similar price as a E500 or 500E W124; and not that many cabriolets were built.

For your viewing pleasure.

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1979 Black on Black, 300CD (sold), 1990 Black 300SE, Silver 1989 Volvo 780, 1988 300CE (vanished by the hands of a girlfriend), 1992 300CE (Rescue).