The originals were tapered and had a sharp angled chamfer onto the titanium centre tube. Later ones were constant diameter rather than tapered, and the chamfer was rounded - this was introduced at the same time as the revised rear free hub taper from a single angle to a double step. These seemed much less likely to fail, albeit I'd still keep the spoke tension as low as possible!No riding involved in this one thankfully. Spotted the crack and removed the hub from the wheel as the rim can have a second life. The hub is toast. Or spares I guess.