A-C-D in the 1930s had included sharing engineering talent. Herb Snow, the vice-president of engineering for Auburn, previously had introduced a rear-drive ladder frame chassis with an X-shaped brace in 1931 with the Auburn 8-98. Snow would later use a similar X-braced ladder frame under the Checker A2. Despite the limited time and fast-paced development time the patented X-Frame continued to set the bar for purpose built taxis. The A2 was a stylish car with pontoon fenders that flowed into the doors, a classic long hood and curvaceous passenger cabin. The body line behind the windshield was comparable with the styling on other classic cars of the period. Missing from the Model A were the driver roof vent, the glass roof and the landaulet opening roof. Model A3 (1947) The following year, in August 1947 Checker introduced another model, the A3. Called a pleasure car, this automobile was Checker's first official entry into the non-taxi market; a car that could be sold into the “Black Car” limo markets that were growing in most US cities. A deluxe version of the A2, the A3 sported a full-width bench front seat, more chrome, and was equipped with a rear trunk. This was the first time Checker had offered a trunk as standard equipment. Since the A2 was designed as a taxi cab, it did not have a trunk. This was because many US cities still had laws on the books that prohibited taxis equipped with trunks. Many of these laws dated back to the prohibition era as rumrunners would transport illegal booze out of sight of the police in the trunks of taxicabs. In 1947, Checker began limited sales of the A3 to the public; previously, Checker sold almost exclusively to commercial operators. Models A4 & A5 (1950) A6 & A7 (1953) Checker introduced the A4 and A5 in 1950, minor updates to the A2 and A3 respectively for the taxicab and limousine markets. Overall length grew modestly to , but both vehicles retained the same wheelbase as their predecessors. The windows, jump seats, and grille were enlarged; the new models had an aggregate increase of of glass area. The A6 and A7 followed in 1953, with the A6 intended for the taxicab market and the A7 as a limousine. For passengers, the primary difference from the preceding A4/A5 was a raised roof to improve rear headroom. Model A8 (1956) When New