It's not often an automaker celebrates its 100th anniversary and Alfa Romeo wanted to do so in style back in 2010. The Italian carmaker reached out to longtime collaborator Zagato (who just celebrated its own 100th anniversary last year) to help it create something very special and ultra-limited. The Zagato Alfa Romeo TZ3 Stradale was the result. Now, here's where things get a bid odd.

Instead of developing its own sports car for the project, which requires time and a lot of money, Alfa Romeo and Zagato went with the Dodge Viper as a base. The Alfa Romeo 4C didn't exist yet. The project was originally commissioned by German collector Martin Kapp who had the idea of doing a one-off build based on the Alfa Romeo 8C, but the Viper allowed for a far more powerful end result.

The Viper's naturally aspirated 8.4-liter V10, which was slightly reduced to 640 horsepower and 585 lb-ft of torque, was still a far more attractive choice than the 8C's 4.7-liter V8 with 444 hp and 354 lb-ft. Numbers don't lie. A Tremec six-speed manual sends all that power to the rear wheels. To keep this TZ3 special, only nine examples were built, one of which is now up for sale from California-based TSG Autohaus.

This example, chassis No. 7, is finished in Brown Metallic with a Chestnut leather interior. Aside from unique badges and special leather, the interior is still pure Viper. It's spent its entire life in Southern California following its return from Milano, Italy. All told, it has just 523 miles on its clock.

The TZ3 features some familiar Zagato styling cues, specifically the double-bubble roof, round taillights, and the rear "Kammback" shape with a unique opening. Needless to say, this thing is an extremely rare find and doesn't come up for sale often.

Speaking of which, how much does it cost? The asking price is $699,000 - more than five times the price of the Viper ACR-X it's based on. How long it'll remain up for sale depends on when a buyer with deep enough pockets can be found.