A necessary accessory to complete the package. But was it worth the money?

Before the modern Nissan GT-R gained its current notoriety, the Japanese marque had the Skyline GT-R R34, which also had the shortest production run from 1999 to 2002. This makes this generation of the GT-R one of the rarest and the last to use the legendary RB-Series inline-six engine.

A few of those Skyline GT-R R34s were more special, though. Through Nismo, Nissan's motorsport arm, less than 20 samples of those Skyline GT-R R34 units were given special attention known as the Z-Tune. All of these were in Z-Tune Silver finish, except for one in Midnight Purple, which was the world's most expensive GT-R – that's before the Nissan GT-R50 by Italdesign was born, of course.

Gallery: Nissan Skyline GT-R R34 Nismo Z-Tune carbon fibre briefcase

However, all samples of the Skyline GT-R R34 Nismo Z-Tune came with a unique carbon fibre briefcase – so unique that the chassis number on the car matches the plaque on its accompanying accessory.

The briefcase wasn't just a novelty, though. It's made with high-quality materials, of course, plus it contains an original Nismo software CD, a diagnostic cable, and a special edition Z-Tune hardcover catalogue that contains never-before-seen road test and beauty images of the rare GT-R.

Now, the R34 Nismo Z-Tune in the video on top of this story was missing its briefcase twin, until it was found under the ownership of a Nismo collector. Fortunately, the collector was willing to let go of the briefcase but at a hefty price: $10,000 (approx £8,100).