No idea about date ranges, but they were using Reynolds 853 and TT OX Platinum. Very high quality steel, and not something you’d get on anything mass market

https://frugalaveragebicyclist.com/2022/05/15/guide-to-vinta...

That Reynolds 853... drool. When I raced mountain bikes a couple decades ago, that was what my hardtail was made of. Just 20.5 lbs for a steel frame bike was nuts at the time, and that bike was a rocket ship.

Still have it. My son wanted to try it one day, his response was "that bike wants to go fast"

Edit: I also had aluminum (too stiff) and titanium frames (too flexible, or floppy as I called it). The 853 was excellent