I don't remember exactly but I believe the fork legs were 0.035" butted down to 0.028". That may be on the thin side though. Could have been 0.043 to 0.035 (seems more likely for a fork)
I didn't weld that many forks. I concentrated on frames and let others - notable George Reynolds, Sue Kirby, and Patrick (sorry on the last name) weld up the bulk of the forks (unis and Yo's)
I did the majority of the box crowns while I was there but those were small numbers and most when with the Team Comps.
If you have access to to an ultrasonic thickness tester, you could find out
Let me know if you do!
I have done a bit of searching around and I have found the numbers .9mm/ .7mm / .9mm quoted a few times . This seems a bit light to me , converting 0.043 and 0.038 is approx 1.1 to 0.9 , that seems a bit more realistic I think.
If I can get my hands on some originals I will try the ultrasonic tester .