In March 1977 a coupé variant of series 123 was presented at the Geneva Motor Show. Types 230 C, 280 C and 280 CE succeeded the 114 series “Stroke Eight” coupés. Their production had run out between June and August of the previous year. As in the preceding Types there was a close technical and stylistic relationship to the saloon. In contrast to the “Stroke Eight” coupés, which were based on the unshortened body platform of their four-door counterpart, the wheelbase of the new two-door cars had been reduced by 85 mm in comparison to the saloons. This measure made the coupé variant stylistically more independent and enabled a more homogeneous and more attractive design. Especially the tail end was now less dominant and therefore fitting in more harmoniously.
But there were not only improvements in design. An important step forward, as against the preceding models, was the even more stable security passenger cell with stiffened roof-frame structure, high-strength roof pillars and reinforced doors. The energy absorption of the front and rear deformation zone in the front and tail end was significantly increased by a controlled deformation capacity. The equipment details of the body corresponded to the upper standard of Types 280 and 280 E, as far as the fitment was in common with the saloons. Thus all three coupé models were provided with rectangular wide-band head lamps, chromed air inlet grills in front of the windscreen and chrome strips under the rear lamps.
As to their mechanical components the coupés were exactly like their four-door counterparts. Like those they had a semi-trailing arm rear axle which had already been introduced in the preceding models. Furthermore, it showed a double-wishbone front wheel suspension with zero steering offset. The braking system, too, was taken over without change from the saloons.
The range of models first consisted of Types 230 C, 280 C and 280 CE. The engines corresponded exactly to the equipment of the respective saloon. In contrast to the preceding model, the 123 coupé was also available with a 4-cylinder engine. Its performance of 109 hp was not of overwhelming temperament, but it provided adequate power.
This could only be said with certain reservations of the Diesel variant which was added in September 1977. The 3.0-liter 5-cylinder engine, known from the saloon, made after all 80 hp. Type 300 CD, however, was only reserved for export to North America. Due to the general speed limits there, no maximum speed was expected. With the development of this unusual, almost bizarre model the goal was achieved to lower the so-called “corporate average fuel economy”, the average consumption of all Mercedes-Benz models offered in the USA. Thus they could correspond to the new consumption limit introduced by the US-government. In September 1979 the performance of the 5-cylinder engine could after all be raised to 88 hp through changes in the injection pump.
Two years later, in August 1981, Type 300 CD was replaced by 300 CD Turbodiesel. It proudly mobilised 125 hp and remained exclusively reserved for export to North America. This change of model was again necessary due to stricter fleet consumption limits. At the same time the saloon, too, had to be replaced. In order to correspond to the new regulations the USA export of Types 280 E and 280 CE was stopped in the model year 1982. The economic turbodiesel which performed only 20 hp less than the emission controlled 2.8-liter petrol-engined car became their successor.
However, changes in the range of engines were also seen in the petrol-powered models. In April 1978, at the same time as with the saloons, the performance of the 2.8-liter injection-engines could be improved to 185 hp by increasing the compression.
About two years later, in June 1980, the 2.3-liter 4-cylinder carburettor engine was replaced by a totally redeveloped aggregate equal in cubic capacity. It was equipped with a mechanically controlled petrol injection and mobilised 136 hp. Thus Type 230 C was replaced in favour of 230 CE which consumed less fuel in spite of a higher performance of 25 %. At the same time Type 280 C with the carburettor engine was taken out of the program.
Furthermore, on demand, both models were now available with ALS (August 1980) and airbag (January 1982).
A comprehensive model improvement package in September 1982, to the benefit of all 123 series models, hardly left any outside traces with the coupés. The rectangular wide-band head-lamps, the most conspicuous characteristic of the improved variants, after all had been part and parcel of the standard two-door car equipment from the very beginning. From the outside the improved coupés could only be recognised by the black (and no more chrome) ventilation louvre in front of the wind screen and maybe by the paint coat if one of the new eight colour tones was used. Several details were changed at the interior equipment.
In August 1985, serial production of the 123 series coupés came to an end. In its eight years of production, 99,884 units had been build, 15,509 of which had a diesel engine. The rarest version of the series was the 280 C with 3,704 units built. Fans of two-door exclusive types had to wait for the successor, the coupé of the 124 series, for more than one and a half years.