of without the need for a tune up, while the second car was put to a 24-hour fuel economy run. It averaged . Series II After the first 10,000 cars were built, the engine was changed to a B-Series, but still of , (as used in the Austin A40 Cambridge). Other modifications that were incorporated at this time were a new gearbox and hydraulic actuation for the clutch (Series I models used a mechanical clutch linkage). The change to a new engine and gearbox added to the weight. This model is referred to as Series II or NK2 (Commencing with Vehicle identification number (VIN) E11001 on August 19, 1954). Series III November 1955 saw the start of Metropolitan Series III (NK3) production (Commencing with VIN E21008 on 28 November 1955). A redesign at this time saw the Metropolitan's B-Series engine increased in capacity to (as used in the Austin A50 Cambridge). Polished stainless steel sweep-spears on the body sides allowed a new two-tone finish to be incorporated, which had the cosmetic effect of lowering, slimming, and lengthening the car. The new exterior colors were P905 "Caribbean Green", P910 "Sunburst Yellow", and P911 "Coral Red" with P909 "Snowberry White" as a contrast. The grille was also redesigned, and the hood had its non-functional hood scoop removed. American Motors changed the designation to "Metropolitan 1500" to differentiate it from the earlier models. The interior was also changed to incorporate a "houndstooth" check material for the seats trimmed with white vinyl. The dashboard was also now painted black, rather than the body color as was the case for Series I and II Metropolitans. The MSRP for Series III models was $1,527 (Hardtop) and $1,551 (Convertible). After VIN E35133 (16 April 1957) the exterior colors were changed to P910 "Sunburst Yellow", P912 "Berkshire Green", and P913 "Mardi-Gras Red" with P914 "Frost White" as a contrast. After VIN E45912 (9 January 1958), the color P910 "Sunburst Yellow" was replaced by P915 "Autumn Yellow" and P908 "Classic Black" was added to the available exterior colors. In September 1957, AMC announced that it was dropping the Nash and Hudson brand names. The Metropolitan was subsequently marketed under the "Metropolitan" name only and sold through Rambler dealers. It is believed that the Nash and Hudson Grille medallions were discontinued around October 1956 (VIN E28326); they were replaced with the "M" style grille medallion. Series IV January 1959 saw