Hi Gerben, I have looked into this type of spring wire, and to be truthful feels it leaves something to be desired...
... It looks as if they used the best available at the time.. It would be interesting to see/know the test results of each components coil spring ... Life, cycle, set, fatigue, failure ... and so on... Also, it looks like most of the coil springs were at the very end of their design parameter.. as in squeezed to solid most every time!! Interesting stuff!.... Thanks again Gerben, best to you, til....lat'r....GT