What's This Metal Tube On This Glorious Classic Skyline GT-R?

Yes, yes, this Hakosuka Skyline is desperately gorgeous, but what's this metal tube running down the roof?

These pictures were taken at a test run in 1970, held at Fuji.

What's This Metal Tube On This Glorious Classic Skyline GT-R?

I stumbled on these sots going through Nissan's Motorsports photo archive, but only when I looked closer did I realize the metal tubing along the back window.

What's This Metal Tube On This Glorious Classic Skyline GT-R?

I genuinely have no clue what it does, but I have a feeling it's pretty awesome. Do you have any idea what it is? I mean, other than some kind of lust-radiating device that makes me want to rob a bank and time/space travel back to a 1970s Nissan dealership?

Photo Credits: Nissan