These cars, and their four-cylinder companion the 12/70, were designed by George Lanchester, who was on the Alvis staff at the time. They were intended to appeal to a slightly wider market, especially business users, and be simpler to manufacture than the Firebird and Silver Eagle models they replaced. A higher proportion of bought-in components was used in their manufacture, although finish was to traditional Alvis standards. Both used engines with block and crankcase cast together in iron, with the timing chain at the front. The Silver Crest was made with 6 cylinder engines of 67.5 x 110 mm, 2362 cc (TF 16.95) and 73 x 110 mm, 2762 cc (TD 19.82).

1937 Silver Crest Holbrook saloon

The name Seventeen was initially used for the smaller-engined car. On the earliest cars a single Solex downdraught carburettor was used on the smaller engine, soon changed to triple SU units as on the larger. Outputs were 95 bhp for the larger engine and 68 for the smaller. These engines were mated to a unit-construction all-synchromesh gearbox of more compact design than that used on the "Speed" models; very good it was too.

1937 Silver Crest Cross & Ellis DHC

Design of the 10' wheelbase chassis was lightened and simplified compared to earlier models. Independent front suspension was by transverse quarter - elliptics and wishbones, whilst at the rear conventional half-elliptic springs were to be found. The rear axle and steering gear were "bought in", from ENV and Burman - Douglas respectively. 16" bolt on wire wheels featured, along with fully compensated Bendix-Cowdrey rod-operated brakes, instead of the Alvis system used hitherto.

Saloon bodies were by Holbrook; four and six light styles being offered. They were comfortable and roomy. Maximum speed was 71 or 80 mph according to the engine fitted. These are very practical cars and it is greatly regretted that so very few survive of over 340 made.Special bodywork was confined to a short run of very pretty dropheads by Cross & Ellis, and a solitary limousine by Charlesworth which happily survives.