Tatra was known for having developed very aerodynamic cars in the 1930s with rear mounted, air-cooled engines. In fact Tatra accused Volkswagen of having based the design of the Beetle on the prototype Tatra V570. See Tatra V570 - Wikipedia, the free encyclopedia . Eventually they settled out of court.
Tatra, being a Czechoslovakian company, was forced to produce only a certain number of cars under the planned economy of the communist Czechoslovakian state after the Second World War. Skoda was 'given' exclusive licence to build passenger cars after the war but the Tatra employees fought with the government to be allowed to continue to produce cars, in addition to the state-mandated production of trucks. The 603 was the second post-war product they made, produced from the '50s until the mid-'70s. It was replaced by the 613, essentially a heavily re-engineered version of the 603 with a more contemporary body. After the Cold War ended Tatra made one last passenger car, the 700. Production only lasted a couple years and few cars were sold.
Tatra now only builds trucks, focusing on the production of heavy-duty off-road models for the construction, mining, forestry and oil & gas industries; they build everything from 4x2 to 4x4, 6x6, 8x8 and even 10x10 models. They're the biggest independent automotive manufacturer left in the Czech Republic (Skoda having been gobbled up by Volkswagen, of course).
It's sad that Tatra was crushed under the communist regime. Unlike most Eastern Bloc cars Tatras were built to very high standards, were of excellent quality and had very innovative designs. By comparison Skodas were plebeian, and most cars from other Bloc countries were cheap knockoffs or licenced copies of other manufacturers' cars (Ladas and FSOs from Russia and Poland were Fiats, Dacias from Romania were Renaults, Moskvitches were mostly copies of Opels, older ZILs were almost exact copies of Packards, etc.).
The ad claims it's a 1976 model but they didn't even begin building the 613-3 until 1985. Its VIN reveals its real age.
The 613 was essentially a 603 with a new body designed in the late 1960s by the Italian coachbuilder Vignale. It retained the rear-mounted air-cooled V8 layout from the T603, however the engine was punched out to 3.5 L displacement and the heads featured double-overhead camshafts; power was up to about 165 hp when introduced. Unfortunately for Tatra the 1968 Soviet invasion of Czechoslovakia and ensuing chaos delayed introduction of the new car until 1974. The slightly revised 613-2 was introduced in 1980, and the 613-3 as pictured here was introduced in 1985. This was the last car made by Tatra under communist rule.