Mercedes is moving full steam ahead on the development of the S-Class Coupe as our spies have caught the model undergoing high-altitude testing.

Mercedes is moving full steam ahead on the development of the S-Class Coupe as our spies have caught the model undergoing high-altitude testing.

Set to be previewed by a concept at the Frankfurt Motor Show, the flagship coupe has a conservative design that bears little resemblance to its sedan counterpart. Notable styling highlights include a single-bar grille, a rakish windscreen and an angular rear end with wraparound taillights and a four-tailpipe exhaust system.

Under the hood, we can expect a variety of familiar engines that are shared with the S-Class sedan. The only notable exception could be an entry-level S400 model with a twin-turbo 3.0-liter V6 engine that develops 333 HP (245 kW) and 480 Nm (354 lb-ft) of torque.

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