For decades, BMW has been known for building the Ultimate Driving Machine. But what do you drive when a factory BMW just isn’t enough? For 50 years now, the answer has been Alpina, a German tuning company that has taken some of the greatest BMWs ever built and added power, luxury, and looks to some of the best cars in the world, and the result has never been boring. While most automakers leave the official tuning of their cars to in-house performance divisions, BMW has worked closely with Alpina for decades to build some of the most unique and unforgettable sports cars in the world.

Before the first M Motorsport team got together in 1972 to build the 3.0 CSL, and before AMG convinced Mercedes-Benz that they needed a go-fast partner with the 300 SEL 6.8 “Red Pig,” Alpina was founded in Bavaria by Burkard Bovensiepen, the son of an industrialist whose father built typewriters under the Alpina name. Bovensiepen moved into one of the buildings in his father’s industrial complex, and began building Weber carburetors for the groundbreaking BMW 1500. Alpina’s reputation for quality and durability was established so quickly that by the end of the decade, BMW had extended its factory guarantee to all Alpina products. By the early 1970s, the tuned cars were making such a name for themselves on the international racing circuit that their roster of drivers read like a who’s who of auto racing, with James Hunt, Jacky Ickx, and Nicky Lauda all driving for the company in Touring Car competitions.

As the company’s star rose in the racing world, Alpina continued to branch out with developing road cars. In 1978, the company developed three BMW-based models in-house, and its turbocharged B7 based on the 5-Series made it the fastest sedan in the world. By 1983, the company was putting so much work into its tuned cars that the German government recognized Alpina as an independent automaker. In 1988, Alpina left racing altogether while BMW’s M division grew exponentially, and as the the company focused on road cars, BMW continued to offer support. After 50 years together, the pair have developed a partnership that rivals the Ford-Shelby bond as one of the most successful performance pairings in automotive history.

For many car enthusiasts, the patented Alpina Blue paint, 20-spoke wheels, and aggressive yet subtle body kits are as instantly recognizable to Alpina as the red, purple, and blue stripes are to BMW’s M-Division. Careful not to have the two performance-based lineups overlap, BMW insists that Alpina focuses on building the ultimate grand tourer, while the M-Division worries about the track – making for one of the most formidable one-two punch combinations in the automotive world.

At BMW’s insistence that they offer only automatic transmissions, Alpina has built some of the best slushboxes in the world, offering a Formula 1-based flappy-paddle gearbox as early as 1992. And while BMW resisted forced-induction engines until recently, Alpina has been using turbochargers of its own design since the 1970s. Outside, unique body kits are designed to keep the cars on the road, and while BMW’s interiors are always tasteful, they can sometimes be accused of being a little too minimal. Alpina’s cars are almost always exciting, offering two-tone upholstery, along with its signature Alpina Blue gauges.

Today, Alpina makes tuned versions of every BMW car between the 3- and 7-Series, as well as a version of the X3 crossover. To celebrate its 50th year in the business, the company is releasing two gorgeous limited-edition models based on the 5-Series and the 6-Series that look like a greatest hits package for the company, and by the time you read this, they could already be long sold out.

Alpina is building 100 cars to celebrate its half-century in the automotive world – 50 examples of the 5-Series based B5, and 50 of the 6-Series B6. The B5 will be split between sedans and wagons, and the B6 between coupes and convertibles. Available in classic Alpina Blue or a dark metallic “Alpina Green,” the cars feature revised bodywork and pinstriping similar to the Alpinas of the 1970s. Inside, the cars are upholstered in black and green leather with piano black wood inserts. Each car has a panel with a unique “1965-2015″ logo and is signed by Bovensiepen, giving each car a direct link to the the company’s storied past.

To prove that the Edition 50 cars amount to more than just a few badges and a new interior, Alpina shoehorned a 4.4 liter V8 under the hoods of both cars, then added two of its own turbochargers to it, giving the B5 models a top speed of 328 kilometers per hour – or over 203 miles per hour. The lighter B6 is a little quicker, maxing out at 205 miles per hour. Revised suspensions and aero kits keep the cars firmly planted to the road well over BMW’s usual factory-limited speed of 155 miles per hour.

Any Alpina is special, but these Edition 50 cars are in a league by themselves. In a world full of outrageous performance tuners, BMW has trusted Alpina to get even more out of its over-engineered cars than it could imagine, and the partnership has lasted 50 years – an eternity for automotive partnerships. With the BMW-Alpina union well into middle age, its shown no sign of slowing down anytime soon, and that’s a very good thing. Alpina has built some of the most exciting road cars of the last 50 years. We can’t wait to see what they have in store for the next 50.

Check out Autos Cheat Sheet on Facebook.