From the early 1960s through the early 1970s, long before BMW became a mass-luxury brand name, the company was known for building cars that combined performance with Bavarian frugality, solid German engineering and attractive -- if sober -- style. By 1966, the marque had embarked on a new mission with the successful 02 series, which included the 1600, 2002, and other two-door variants.

Yet their customer's taste for sporting luxury would never be sated by the boxy 02. Coincidentally, BMW had a perfectly delightful inline-six engine with which to power a more substantial car. Called the E9 series, it was designed by Wilhelm Hofmeister, and began as a 2.8-liter version called the 2800 CS in 1968. The later 3.0 CS and 3.0 CSi, made from 1971 through 1975, have since become quite collectible.

That car eventually morphed into a lightweight called the 3.0 CSL, which was never imported to the United States when new. Made from 1971 through 1975, it was a homologation model developed by engineer Jochen Neerpasch for competition in the European Touring Car Championship, which the CSL won in 1973, and every year from 1975 through 1979. The ultra-rare 3.0 CSL "Batmobile," produced from 1972 through 1975, made a then-impressive 206 hp, and achieved a top speed of 137 mph with its full aero package.

The E9 was powered by BMW's M30 engine, a 2,986 cc, SOHC inline-six that developed about 180 hp in the carbureted CS and 200 hp in the fuel-injected CSi. A robust, under-stressed and reliable design, it was mated to a four-speed manual transmission or a three-speed automatic. The CSL had a 3,003 cc engine, allowing it to run in the over-three-liter class, and for 1973, was enlarged to 3,153 cc.

Excepting the "Batmobile," every E9 exudes a refined understatement. Its lines -- especially in profile -- are emphatic yet simple, with subtle contours enhanced by delicate A and C pillars allowing expansive glass all around, one reason these cars are so brilliant to drive. Notably, the E9 has no B pillar, allowing uninterrupted front and rear-quarter windows, that, when lowered, make the car in profile look light as a feather.

Overall, the E9's proportions are perfectly balanced and harmonious in a way few car designs have equaled. Brightwork, while minimal, adds a touch of flair to the broad expanses of painted body surface. Front fenders are punctuated by purposeful and attractive vents that hint at the performance lurking under the hood.

The interior is positively luxurious compared to the spartan 2002 series, elevating this BMW to flagship status within the brand. Big doors make entry and exit a breeze, and the airy, spacious cabin offers nearly 360 degrees of unencumbers views. Comfortable front bucket seats were available in fabric or leather, with two rear bucket seats that add to the sporting character of the car. Generous wood veneer on the dash and door panels adds a touch of luxurious warmth that elevates the experience for driver and passengers.

With the exception of aluminum doors, hood, and trunk lid on the CSL, all E9s are made of steel. The bodies were made by Karmann, and are known for a propensity to rust (especially check the front wheel wells), so, as with most cars of the era, careful inspection prior to purchase is crucial, and can mean the difference between pleasure and great financial pain.

Because many examples have seen "improvements" made by prior owners over the years, would-be owners will have to decide whether a factory-stock or a modified car is to their taste. Period-correct and attractive Alpina wheels are frequently added, but more extreme suspension, drivetrain, and interior upgrades are often encountered, some tasteful and others less desirable. The latter include, in our opinion, oversized wheels and radically lowered suspensions.

A concours "Batmobile," the ultimate iteration of the E9 series, can fetch $550,000. Fortunately, more than 30,000 examples of all E9 models were made from 1968 through 1975, with values for the 3.0 CS and CSi ranging from $60,000 for a good CS to $190,000 for a concours CSi. Thus, there are plenty of options, depending on one's budget and intent.

Many BMW enthusiasts would rightly argue that the elegant E9 represents BMW's most beautiful design, and is one of the most rewarding "old" models to drive. That the 3.0 CS and CSi were made to be superb daily drivers in their day makes them a top choice for collectors looking for a comfortable, reliable, and beautiful classic that only seems to get better with age.