When I was a kid, a cereal box top and 15 cents would get you a genuine decoder ring. I need some of that code-cracking jewelry now, because I'm driving a test car that bears one of Infiniti's new model designations: the Q60S CPE LTD 6MT.

Honestly, that's what the window sticker says. Clearly, this is nomenclature whose meaning is readily accessible only to the Infiniti high command. Competitors, customers, car writers, and U-boat captains will not be able to crack the code unless, of course, they have a decoder ring.

Fortunately, I still have one and was able to decipher most of the Monroney message. The S model suffix stands for Sport, CPE for coupe, LTD for Limited, and 6MT for six-speed manual gearbox. As for the Q60 model designation, that remains encrypted. All we know is that, unlike its predecessor, the 3.7-liter G37, it has no alphanumeric significance.

So what we have here is a performance-minded version of an Infiniti coupe that is a lot more fun to drive than it is to name.

The Q60 is essentially a Nissan 370Z sports car that's been stretched 16 inches to create a 2+2 luxury coupe. It uses the same 330-horsepower, 3.7-liter V-6 found in its G37 predecessor and the 370Z. Transmission choices include a seven-speed automatic or the nifty, six-speed manual I was so happy to find in the tester.

This handsome, athletic coupe is turned into the even more performance-minded S version by adding sport-tuned suspension, steering, and braking systems. The S is also individuated by a black grille, wheels, and rear spoiler.

This car is a looker. Its sculpting eschews edginess in favor of rounded, flowing surfaces, but it exudes sufficient muscularity and aggression largely with its stance and strong haunches. And certainly, the macho quotient isn't diminished by chrome exhaust tips nearly the diameter of water mains

The pleasing aesthetics continue indoors. Clean, fresh design made the tester's innards one of the most appealing Infiniti interiors I've seen.

Swooping bright metal accents bisected the car's black door panels. The black leather seating surfaces had perforated inserts flanked by red-stitched, smooth leather surrounds. The dash's bright metal center stack was businesslike instead of busy.

The sour note: The rear window sills and most of the console were hard plastic, which shouldn't be the case in a $50,000 car.

Like any 2+2 coupe I can think of, the Q60S has a cramped backseat. And at 7.4 cubic feet, its trunk is teenie-weenie.

Then again, people don't buy sporty rides like the BMW 4-Series, the Lexus IS, the Audi A5, and the Q60S to haul Little League teams and garden mulch. They buy them because they're fun to drive - and the Q60S is.

Though its torque output (270 pounds) isn't quite in a league with its hefty horsepower rating (it is neither turbocharged nor direct injected), this limited-slip-differential-equipped rear-driver accelerates well. And there's a nifty exhaust note to go with that oomph.

It also handles very well. A sport-tuned suspension and wide, 19-inch performance rubber let the car stay flat and planted in rigorous corners, and make a winding road a memorable treat.

The steering is quick, and when those discs get squeezed by equally large brake calipers, the show shuts down in a hurry.

Weighing in at a little more than 3,600 pounds, the Q60S manages EPAs of 17 city and 25 highway, which aren't horrible for a performance car. And given the way the car is equipped, it is a pretty decent value at a base price of $47,700.

Excellent

2015 Infiniti Q60S CPE LTD 6MT

Base price: $47,700.

As tested: $49,575.

Standard equipment: 3.7-liter engine; six-speed manual gearbox; rear drive, sport suspension, braking and steering, and a nice amenity list ranging from glossy black alloy wheels to a moonroof, leather, navigation, and a Bose sound system.

Options: Include pearlescent paint, trunk mat, illuminated kick plates.

Fuel economy: 17 city and 25 highway.

Engine performance: Lively.

Handling: Top shelf.

Ride comfort: Surprisingly good.

Styling: Engaging.

Warranty: Four years/60,000 miles bumper to bumper.

The Ben key: four Bens, excellent; three Bens, good; two Bens, fair; one Ben, poor.

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