No, not TIG welded but fillet brazed (or "bronze welded" in British parlance) by Trusty in England. Tubing is straight gauge chrome-moly, 0.5mm IIRC. The bottom bracket shell is unthreaded and used pressed in cartridge bearings with an untapered spindle held in place by circlips. The fork was solid cast aluminum, with a steel steer tube pinned in place to a plug on the top of the crown. This was the source of the problems with the forks -- the pin site was a stress riser and could fail without warning.