Admirers of the Porsche 911 would insist that no other model in the auto industry has stayed so true to its original formula, a production life span that is closing in on 50 years. Yes, the Chevrolet Corvette celebrates its 60th anniversary this year, but the muscle-bound 2013 version is hardly cut from the same cloth as Harley Earl's tepid roadster of 1953.
The 911, on the other hand, still carries the distinctive profile of the model that made its debut at the 1963 Frankfurt motor show. Its engine is still an opposed 6-cylinder, and it is still placed at the rear.
One thing that's not the same is the model name: initially, the new Porsche was labeled the 901, but the road car was renamed the 911 because a French automaker, Peugeot, held the rights to three-digit model names with a zero in the middle.
At the time, Porsche's visionary designers could hardly have imagined that their sports car would still be thriving and evolving a half-century later. Although the 911 has added weight and girth over the years, it has also been transformed, continuing as a benchmark for all-around performance.
Porsche did not start out as an automaker, but as an engineering firm doing design work for other companies. It began making its own sports car, the 356 model, in the late 1940s, amid the rubble of postwar German. Based heavily on the design of the humble Volkswagen Beetle, the Porsche 356 established the company as a producer of well-engineered, high-quality cars, its reputation bolstered by racing successes.
Ferdinand Porsche, the genius who founded the company, died in 1951, but his son, known as Ferry, was firmly at the helm. As competition increased, Ferry and his talented staff felt the need for a new-generation car to replace the aging but still-popular 356, so in the mid-1950s they set out to develop a slimmer shape with a stronger engine.
Some of their early efforts involved dusting off partly developed plans from earlier years. An awkward notchback prototype was considered, but Ferry's son, F. A., known as Butzi, responded with a sleeker, more contemporary version of the Porsche coupe sketched by the company's original stylist, Erwin Komenda, in the 1940s.
The family business also included Ferry Porsche's nephew, Ferdinand K. Piëch, a promising young engineer who conceived the seven-bearing crankshaft and overhead-cam layout that endowed the 6-cylinder 911 engine with its rapid-revving sports-car personality.
The 911 also benefited from a racing-derived lubricating system that prevented engine damage.
With improvements in tires, brakes and suspension systems, cars were now able to corner and stop so hard that the engine would starve for lubrication as oil sloshed away from the supply tube of the circulating pump. To prevent this, the 911 engine was given two oil pumps, one to keep a reservoir tank full of oil and a second pump to feed oil from the tank to the moving parts, regardless of cornering, acceleration or braking forces. This so-called dry-sump system also eliminates the deep oil pan that normally hangs below the engine, making it possible to lower the mounting point and improve handling.
The Porsche 911 was not perfect, although many considered it bulletproof. Early on, the tensioners for its cam chains were prone to failure, often with near-catastrophic results. And the car had a disconcerting habit of oversteering, especially when a novice driver would suddenly let off the gas pedal in the middle of an exuberant turn.
While expert drivers used this quirk effectively, steering through curves with the throttle, less experienced pilots spun out in short order. In recent years, modifications by Porsche engineers, including electronic stability control systems, have made the 911 more forgiving.
As the road-going 911 evolved, it became more powerful and luxurious, but also heavier. For this reason, many enthusiasts feel that some of the earlier models -- 1969-73 cars in particular -- are the most fun to drive and more desirable to collect.
"The 911 Porsches built after 1973 became heavier," said Dennis Frick, owner of Europa Macchina, a Porsche restoration business in Lewisberry, Pa., "and the pre-1969 cars simply aren't as good."
At the same time, Mr. Frick points out, some later 911s are desirable for their luxury features, overall reliability and easy-to-drive engine and transmission. This is especially true of the 1987-89 cars.
Some 911 models desirable to collectors command stratospheric prices. For example, the limited-production RS, a rare high-performance 911 offered in the early 1970s, is a six-figure car in decent shape, while other 911 models of that era usually fall into the $30,000 to $70,000 range.
One of the most sophisticated, high-tech versions of the 911 was never officially sold in the United States. With its twin-turbo engine and slippery shape, the 959 was the fastest street-legal production car in the world when it was introduced in the mid-1980s, and its impressive all-wheel-drive system was later used on the Carrera 4 and Turbo models.
Many enthusiasts favor the 993, the factory's designation for the last 911 generation with an air-cooled engine. It's not uncommon to see a good 993 sell for more than the later water-cooled 996 models.
Whether first-timers or experienced collectors, 911 buyers' most common mistake is to be swept away by the allure of a good-looking car, buying it without first having an expert put it up on a lift and look carefully at the underside. Beginning with 1976 production, Porsche used zinc-coated steel for the entire 911 body shell. This galvanized coating greatly reduces the chance of rust.
For a time in the 1970s, well-intentioned Porsche managers laid sound plans to replace the 911, a rear-engine outlier, with a new generation of traditional front-engine sports cars, beginning with the 4-cylinder 924 and the more luxurious V-8-powered 928. But the outspoken loyalty of its 911 customers surprised even the Porsche managers. Sales of the 911 remained strong, while these front-engine models got a lukewarm response and were eventually discontinued.
Although the price of admission isn't cheap, 911 owners are surprisingly diverse, albeit largely male.
When Rod Heckman worked in the corporate world and got a $25,000 signing bonus, he asked himself, "What would be the most fun of any gift I could buy myself?" He fell in love with a 911 convertible, which he has owned for the last 20 years.
Harriet Sparkler first bought a less expensive Porsche Boxster, later replacing it with a 911. "In my mind, the Porsche brand is considered the best," she said. "When I test-drove the 911, it had such a wonderful feel. Among other things, the clutch seemed so much nicer than my Boxster."
Sometimes described as "a car everybody wants and nobody needs," there's no question that 911 sales are vulnerable to the ups and downs of the global economy, and yet it has survived deep recessions that killed many other sports cars. As a textbook example of industrial design that has progressed to keep pace with design trends, with each new model reinterpreting its heritage yet resisting retrograde shifts, the classic, beloved shape of the 911 has endured. It remains Porsche's core model line, if not in sheer numbers, certainly in desirability.
This article originally appeared in The New York Times.