These grades began at a very common type of steel known as A36, which has a yield strength of 36ksi (or kilopounds per square inch), and got progressively stronger -- all the way up to steels that had yield strengths of 100ks
They claim the steel was made in Luxembourg - the company that made it, however, is called Yawata Iron and Steel.
Gets bigger.
Kobe Steel?
Banovic, S. W., et al. "The Role of Metallurgy in the NIST investigation of the World Trade Center Towers collapse." JOM. (Sept. 8, 2011) http://www.tms.org/pubs/journals/JOM/0711/banovic-0711.html
They claim the steel was made in Luxembourg - the company that made it, however, is called Yawata Iron and Steel.
Yawata Iron and Steel became Nippon Steel. https://www.nipponsteel.com/en/company/about/history/
According to this Yawata was operating a Kobe Steel facility from 1966 to 1976.
WTC - The core complex was built between 1966 and 1975
What are the chances?