240Z: Adjustable competition suspension springs + NISMO suspension (re)discovered

About year ago, I managed to find a complete set of somewhat rare Nissan height-adjustable competition suspension.

Back then, I discovered that one of the rear springs was shorter than the other one, which was a bit strange.

The catalogue however clearly mentions 205,5mm’s free length, for both sides, on the rear springs 55020-E4621:

The difference might have occurred due to wear under racing use, or long-term storage in compressed state or whatever, but yeah it was a bit strange. My thinking was that I probably would not sense a big difference once they are installed in a compressed state, so it didn’t really bother me. But then, I came across these for sale: A NOS set of 55020-E4621 springs. It’s probably not often you will see a set of unused springs for a competition adjustable suspension, still new in its original box, with all the stickers still on it.

So I HAD to get them:

Once unpacked, you can clearly see that the two old ones on the left side had been repainted at some point with a flat black (vs glossy black on the new ones) and that indeed one spring was shorter:

That means, that my adjustable competition suspensions is pretty much complete now and ready to be overhauled. Excellent. And a bit unexpected, but I’m more than happy.
But that’s not it. While going through the boxes to put together the suspension for the Photos, I opened a box of spare parts that came with some of the suspension parts. I remember it had some unknown springs and strut inserts inside. Back then I removed one of them from the packing and could only read “KYB” (= Kayaba Brand) and a part number. I quickly googled the numbers back then to find out what it was, but couldn’t find any information, so I just put them back in the box as “random aftermarket” parts that came with some other stuff.

Well today I was about to through them in the bin, since I had no use for them, but inspected them a bit closer before scrapping them. And…? I just found out it’s actually a set of NISMO dampers in still quite good shape:

56110-RRE72 and 56210-RRE72. The springs have no markings on them, so not sure if these are NISMO too, or any other aftermarket or OEM springs.

I tried to find the part numbers in my various old NISMO / Nissan Motorsports / Competition catalogues, but wasn’t able to find them. A quick google search pointed my towards my own suspension post on this very website, where I showed a similar set with the same part numbers that was Sold on Yahoo auctions years ago specifically for the S30. I’mm still trying to find out more. The NISMO logo tells me that it must have been in the 80ies / early 90ies that this set was sold. But I’d like to find out what specification it has, and for what specific type of racing it was designed. If you have any input on this specific dampers and the springs that came with it. Please let me know.

Update: Thanks to Alan, I was able to get confirmation that they’re listed in the 1997 NISMO catalogue, with the corresponding specifications and details.
According to the manual, these are a static suspension setup, that is based on the above height-adjustable suspension. Quite cool!